FlSSURELLID^E.] 



MUSEUM OF ANIMATED NATURE. 



247 



The living species are very numerous ; M. Des- 

 hayes enumerates thirty-three living, to which 

 must be atlded twenty-nine species described in 

 the Proceeds. Zool. Soc. 1834, p. 123 et seq., by 

 Mr. Sowerby — two excepted, one by Mr. Frembly, 

 the other by Mr. Gray; — all from the south-west 

 coast of America, and the islands of the South Pa- 

 cific Ocean. Of fossil species M. Deshayes gives 

 eight as the number in tertiary deposits. Of these 

 eight, three species are also living, viz. Fissurella 

 Grai'ca and F. costaria in the Mediterranean and 

 other seas of Europe, and also in the Indian seas, 

 and F. neglecta, a native of the Mediterranean. It 

 appears that another species, F. Noachina, still ex- 

 tant in the northern seas, occurs in a fossil state in 

 Sweden and Norway. It is a link between Fissu- 

 rella and Emarginula. The genus Emargiimla pre- 

 sents nearly the same characters as Fissurella, ex- 

 cepting that the shell, instead of having an aper- 

 ture at the summit, has an anterior fissure corre- 

 sponding to a similar fissure in tlie mantle, which 

 leads to the branchial cavity. This fissure is some- 

 times marginal, sometimes in the middle of the 

 back of the shell. The edsres of the mantle envelop 

 and cover to a great extent those of the shell. The 

 conical tentacles have the eyes seated on a tubercle 

 at their outer base. The edges of the foot are 

 fiinged with iilaraents. 



The shell is not regularly conical, but is very 

 abrupt posteriorly, often even concave, with the 

 apex bending backwards. Fig. 2830 exhibits in 

 outline the animal and shell of Emarginula. Fig. 

 2831 represents the shell of Emarginula conica, in 

 which the fissure is marginal. 



2832. — De Blaisville's Ejiargiscla 

 (Emarginula Blahaillii). This species is an ex- 

 ample of a group of Emarginulae in which the fis- 

 sure is remote Irom the anterior edge of the shell, 

 approximating tow ards the apex. 



2833. — The Common Emarginula 



{Emarginula fissura). Patella fissura, Linn. The 

 Emarginula fissura is a native of the seas of Europe, 

 and aftords an example of those species which are 

 distinguished by a compressed form, with the ante- 

 rior border deeply notched, and the summit stronijly 

 marked, a, the natural size; 6, magnified; c, the 

 magnitied shell turned up, shovvmg the animal in 

 iitu. 



2834. — The Emarginate Emargixcla 



(Emarginula emarginata). In this species we have 

 an example of a group in which the form is still 

 more compressed, Uut in which the anterior border 

 is only bent into a gutter ; the summit is still pro- 

 minent. 



2835. — The Depressed E.mabginii,a 



(Emarginula dcpressa). This species of Emargi- 

 nula represents a group, in which the form is much 

 depressed, the summit very little developed and 

 almost centrical, and the notch marginal but small. 

 M. de Blainville has separated a group from Emar- 

 ginula, and elevated it to the rank of a genus, under 

 the title of Parmophorus. The Parmophori, says 

 Cuvier, have, like the Emarginiilas, their shell in a 

 great measure covered by the reflected edges of the 

 mantle ; the shell is oblong, slightly conical, and 

 equally destitute of orifice or notch ; the branchiso 

 anil general organization are the same as in Fissu- 

 rella. 



Whether the Parmophori are separated from the 

 Emarginulae on good ground appears to be very 

 questionable. M. Deshayes. in the last edition of La- 

 marck (183G), makes the following observations : ~ 

 " Cuvier was the fiist who gave anatomical details 

 of the genus Emarginula ; and he made it appear 

 how much analogy there existed between it and 

 Fissurella. Sufficient differences nevertheless exist 

 between these two genera to warrant their adoption 

 in systematic arrangements. But the same does 

 not ho!d good with respect to the genus Parmo- 

 phorus. M. de Blainville, to whom we owe this last 

 genus, and who was the first to make the animal 

 Known, had judiciously preconceived the necessity 

 of its junction with Emarginula. In fact, not only 

 liave the animals of the two genera a perfect ana- 

 logy (affinity), insomuch that in some instances it is 

 difficult to distinguish between them, but the shells 

 themselves, as might have been supposed a priori, 

 in some cases offer passages from one genus to the 

 other, the number of which will be augmented by 

 additional discoveries. When we have before us a 

 fairly complete series of living and fossil species, 

 belonging to the two genera, the following train of | 

 remarks suggests itself; namely, the two fossil spe- : 

 cies of Parmophorus have no trace of a marginal '■ 

 notch ; Parmophorus Australis has the anterior i 

 border a little depressed in the middle, and, corrc- ! 

 sponding with this depression, a small crest is to be ; 

 seen within the shell, indicating the separation of the 

 mantle. Further, among the species of Emarginulae 



brought home by MM. Quoy and Gaimard, there is 

 one which they name Parmophoida, and which 

 would seem to be deprived of a marginal notch. In 

 the Subemarginulae of M. de Blainville the shells 

 have no longer this notch, but they have, within, a 

 deep furrow (sillon) in place of it. In other species, 

 as Emarginula rubra of Lamarck, and Emarginula 

 elegans of Defrance, the small interior furrow is 

 terminated on the border by a very short notch, 

 and from this commencement (presenting the first 

 trace of a fissure) to the termination of the series of 

 species, we see this notch become deeper and deeper, 

 and change at last into a deep slit occupying one- 

 half of the height of the shell." M. Deshayes then 

 proceeds to comment on the differences of the shells 

 in other respects, as far as external fo:m is con- 

 cerned, observing that, while from the general aspect 

 of the shells the zoologist is induced to separate the 

 genera, the structure of the animals themselves, on 

 the contrary, forbids such a separation, as it affords 

 no structural data on which the two genera can be 

 respectively established. He adds that Mr. Sowerby 

 has come to the same conclusions, and in his 'Genera 

 of Shells' has united the Parmophori to Emarginula, 

 an arrangement which other naturalists will, he 

 doubts not, regard as warranted. 



2836. — The Austkai. Parmophorus 

 (Parmophorus Australis). Emarginula Australis. 

 In this example of M. de Blainville's genus Par- 

 mophorus, now merged into Emarginula, the shell 

 is much compressed, and striated concentrically. 

 It is a native of the seas of New Holland, New 

 Zealand, &c. 



In their habits the Emarginulae resemble the Fis- 

 surellse ; they frequent rocks, at depths ranging from 

 the surface to eleven fathoms. 



With respect to fossil Emarginulae Mr. G. B. 

 Sowerby, in his ' Genera of Recent and Fossil Shells,' 

 observes that they are scarce ; they occur however, 

 he adds, " in the calcaire grossier and its contem- 

 porary strata, in the crag of Suffolk, Essex, and 

 Norfolk, and in the Bath oolite. They are very 

 elegant little fossils, particularly Lamarck's Emar- 

 ginula clypeata. We cannot consider his Parmo- 

 phorus elongatus as a species of this genus, for its 

 vertex is anterior, as its muscular impression de- 

 monstrates. Consequently we find in it no mark of 

 a canal at either end ; it must therefore be classed 

 with Patella." 



M. Deshayes in his tables enumerates seven living 

 species of Emarginula, and eleven fossil species, 

 from tertiary deposits : one, the Emarginula fissura, 

 is both living and fossil ; it occurs in the seas of 

 Europe, and is found fossil in the crag at Bordeaux 

 and Dax, and also near Paris (Pliocene, Miocene, 

 and Eocene periods of Lyell). De la Beche records 

 two species in the blue marls of the south of France ; 

 one the E. reticulata of Sowerby, the other closely 

 approaching the E. fissura. In the cretaceous 

 group, De la Beche enumerates two species, E. 

 sanctae Catharina; and E. pelagica, both from 

 Rouen. In the oolite group he records one species, 

 E. scalaris, Sowerby, from the great oolite at An- 

 clifF, Wilts. 



M. Deshayes, in his edition of Lamarck, 1836, enu- 

 merates eleven species living, and only five occur- 

 ring in a fossil state. The latter are E. costata and 

 E. clypeata, from Grignon ; E. radiola, from Par- 

 nes ; and E. elegans, and E. clathrata, the first 

 from Paris and Valognes, the other, a rare fossil, 

 from Parnes. 



With respect to Parmophorus of De Blainville, M. 

 Deshayes in his tables gives two living and several 

 fossil species, the latter from tertiary deposits. Of 

 these, one is from Touraine, where it occurs in 

 the Miocene beds of Lyell. He enumerates two 

 from the crag ; three from Touraine ; three from 

 Angers ; five from Paris ; and two from Valognes. 



In his edition of Lamarck, only two species are 

 noted as fossil, one the P. elongatus, which with a 

 variety occurs at Grignon; the other P. angustus, 

 from Paris. 



Before we leave the family FissurellidsB, we may 

 revert to the observations with which weintroduced 

 it, namely, that M. de Blainville places it with the 

 true limpets (Patella), in the same order (cervico- 

 branchiata) ; whereas Cuvier disjoins this family 

 from the limpets entirely, and that on the differences 

 observable in the characters of the branchial appa- 

 ratus. 



M. de Blainville, indeed, maintains that in both 

 groups the organs of respiration are in a cavity 

 situated above the neck ; that they exist in the 

 form of pectinations in the P'issurellidae, and in the 

 form of a net or delicate raeshwork on the roof 

 (plafond) of the branchial cavity in the limpets, 

 whence he terms them lletifera. On the contrary, 

 Cuvier considers that the branchial organs of the 

 limpet exist in the form of a fringe of filaments, 

 forming a cordon under the edge of the mantle. 



These two opinions are at perfect variance with 

 each other ; and if Blainville be correct, the ar- 



rangement of Cuvier must be defective. Assuming 

 for the present, however, that Cuvier is right in his 

 opinion, we shall follow him in assigning the Pa- 

 tellae to a distinct situation from that in which the 

 Fissurellidae are placed, and when we come to the 

 family Patellidoe, the first of the succeeding order, 

 endeavour to give an outline of the observations of 

 some of those conchologists who have investigated 

 the subject. 



ORDER CYCLOBRANCHIATA (Cuv.). 



The Cyclobranchiate mollusks have the branchisB 

 in the form of little foliations, or pyramidal bodies 

 like filaments, attached"en cordon," or in a row more 

 or less complete, under the edge of the mantle, 

 nearly the same as in the Inferobranchiata, from 

 which they are to be distinguished by their bisexual 

 structure, each individual continuing the race inde- 

 pendently. The heart varies in situation, but is not 

 traversed by any part of the intestinal canal. 



In a note (see 'llegne Animal,' vol. iii. p. 113) we 

 learn that the Cyclobianchiataof Cuvier are not the 

 Cyclobranchiata of M. de Blainville. Cuvier says, 

 " M. de Blainville, who terms the order in which 

 he places Doris" (one of the Nudibranchiata of Cu- 

 vier) " Cyclobranchiata, makes of the genera Fissu- 

 rella, Emarginula, and Parmophorus, and of the 

 Patellae, an order which he names Cervicobran- 

 chiata; and which he divides into Retifera and 

 Branchilera. The lletifera are the Patellae, because 

 he supposes that they respire by means of a network 

 on the roof of the cavity which is above the head. 

 I have not been able to discover or see any other 

 organ of respiration besides the cordon of foliation 

 which runs all round under the border of the mantle. 

 See the anatomy of the Patella in my memoirs on 

 the mollusks." These observations bring us to the 

 first family : — 



Family PATELLID^ (Limpets). 



The PatellidaD, according to Cuvier, have the entire 

 body covered with a shell in the form of a widened 

 cone ; under the borders of the mantle runs a cordon 

 of small branchial foliations; the head is furnished 

 with a short and thick proboscis, and two pointed 

 tentacles having the eyes at their outer base. The 

 mouth is fleshy and contains a spine-armed tongue, 

 which is continued backwards and folded deeply in 

 the interior of the body. The stomach' is membran- 

 ous ; the alimentary tube, long, slender, and very 

 much folded ; the heart is placed forwards above 

 the neck, and a little to the right. 



To this detail of characters we may add a remark 

 by Mr. G. B. Sowerby (' Genera of Recent and Fossil- 

 Shells') : he says, " There is no canal for the passage- 

 of water to the branchiae, as there is in Emarginula. 

 and Siphonaria, for in this genus (Patella) the bran- 

 chiae are external, surrounding the animal." The - 

 want of access to a branchial cavity, if it existed 

 with its vascular network, is out of the question. 



If we consult Rang, who follows Cuvier in his . 

 description of the mollusk of Patella, we find that 

 he makes the following observation : " M. de Blain- 

 ville believes that he has perceived the branchiae of ' 

 the Patellae in a vascular network attached to the 

 plafond of a branchial cavity. Not having been 

 able to distinguish this network, we think with Cu- 

 vier that the organ of respiration shows itself in 

 these animals in the circle of leaflets, which sur- - 

 rounds the body, between the foot and the mantle, 

 as in the Phyllidians" (Inferobranchiata). 



This circle of leaflets being always exposed to the 

 action, no branchial cavity is needed, and, as they 

 are covered with minute cilia, they maintain a per- 

 petual current over their surface, flowing from the 

 outer to the inner edge, and thus fulfil the office of ' 

 branchiae. 



M. Deshayes, in his edition of Lamarck's 'Ani- 

 maux sans Vertebres,' makes some valuable remarks • 

 on the structure and natural affinities of the PatellECr- 

 in which he supports, with irrefragable arguments,-, 

 the views of Cuvier, and points out the causes vvhichi 

 led to M. de Blainville's mistake. 



More recent observations confirm the correctness 

 of these views, and demonstrate the truth of Cuvier's 

 opinions. Fig. 2837 is a representation of the animal 

 of Patella. The Patellae are widely spread. They 

 exist in every latitude, excepting in those of the 

 arctic seas : many are common on the coasts of 

 Europe, but it is in the hotter regions that they are 

 most numerous, and display the largest dimensions. 

 In their habits they are littoral, frequenting rocky 

 coasts, where they are found fixed upon stones, reefs, 

 and large shells ; many crawl about, continually 

 changing their resting-place, but some seem to be 

 long stationary in one spot, to which they closely 

 adhere. The depth at which they are found varies 

 from the surface to thirty fathoms. They are said 

 to live upon fuci and other sea-weeds, the substance 

 of which is easily broken up by the action of their 

 rasp-like tongue ; yet we cannot imagine how such 



