829 



FISH-LICE. 



FISSURELLID^E. 



830 



pointed teeth fringed the lips, and within this row another, whose 

 bulk was at least twenty times as great. The other genus, Meyalich- 

 thys, was perhaps more strikingly characteristic of the next succeeding 

 period, during which the Carboniferous Limestone and Coal were 

 being deposited ; and it may therefore be as well to postpone for the 

 present any description of it." 



(Owen, Lectures on Comparative Anatomy, vol. ii. ; Yarrell, British 

 Fishes ; Agassiz, Recherches mr les Poissons Fossiles ; Agassiz, Report on 

 the Fossil Fish of the Devonian System ; Transactions of British Asso- 

 ciation, 1842 ; Richardson, Report on the present Stateof the Ichthyology 

 of New Zealand, ib. ; Agassiz, Synoptical Table of British Fossil Fishes, 

 ib. 1843 ; Agassiz, Sur let Poissons Fossiles de VArgile de Londres, ib. 

 1844.) 



FISH-LICE. [CAUCUS.] 



FISHES, FOSSIL. [FiSH.l 



FISHING-FROG. [Lopnius.] 



FISSIROSTRES, the Swallow Tribe of Birds, distinguished by a 

 very broad bill with a very wide gape, and small and feeble feet. 

 They belong to the order Insessortt, or Perchers, and take their food 

 on the wing. [HIRUNDINID^; ; INSESSORES.] 



FISSURELLID.E, a family of Prosobranchiate Gasteropodous 

 Mnllusca. This family constitutes a very natural transition from 

 the Limpets [PATELLID^E], to the completely spiral univalve shells. 

 All the species of this family are remarkable for some solution of 

 continuity in the shell, either a perforation or a slit in the region of 

 the vent. The form of their shells is more or less conical, with 

 indications of a rudimentary spire at the apex, which often disappears 

 with increasing age. The animals have well-developed heads, with 

 short muzzles and subulate tentacles, at the external bases of which 

 are the eyes placed on rudimentary pedicles. 



This family embraces the genera Fisiurella, Emarginvia, Punctu- 

 retta, Parmophorus, and Rimuia. 



The Fiisurellce, which Cuvier places among the Scutibranches, his 

 seventh order of Gasteropoda, have a large fleshy disc or foot 

 beneath the belly, like the Patella, and a conical shell fixed upon 

 the middle of the back, but not always entirely covering it, for this 

 shell is pierced at its summit with a small aperture, generally oval, 

 which, according to Cuvier, serves at the game time as a passage for 

 the water necessary to respiration and as an outlet for the excrements. 

 This aperture penetrates into the cavity of the branchuc situated on 

 the fore part of the back, and in the bottom of which the vent 

 discharges itself. This cavity is, besides, widely opened above the 

 head. There is on each side, symmetrically disposed, a pectinated 

 bronchia or gill. The tentacula are conical, at the external bases of 

 which the eyes are situated. The sides of the foot are fringed with 

 filaments. Dr. Gray says, " In the young state of the Fissurellce, 

 the hole by which the faeces pass out of the shell is placed a little 

 in front of its recurved and spiral apex ; in this state it has been 

 formed into a genus under the names of Rimuia and Puncturella. 

 But as the animal grows, the hole enlarges in size backwards, and 

 the true apex being absorbed, the hole appears in the adult shell 

 to be placed on the tip, and in some species even to extend 

 behind it." 



The muscular impression ia in the form of a horse-shoe, with the 

 opening in front. 



Animal of Fisiurella. 



Shell of Fintirella. 



De Blainville thus arranges the genus : 



o. Species which have the middle part of the borders of the 

 opening excavated as it were, so that when placed upon a flat 

 surface, they only touch it at their extremities. Ex. Fissure!'" 

 nimbota. 

 Deshayea observes that the synonymy of this species hag been 



very faulty from the time of Linnaeus downwards ; and he remarks 

 that three species are confounded under Patella nimbosa in the 12th 

 edition of the * Systema Natura).' Deshayes adds that the species 

 was named in Lamarck's collection, and that he has seen it, and 

 therefore knows what Lamarck meant by his Fissurella nimbosa. 

 The figure from which our cut is taken, that of Martini I. t. xi. 

 f. 91-92, is one of those references which Deshayes would leave 

 untouched as indicating the species. 



Fissurella nimbosa. 



. Species more depressed, &c., so that when placed upon a flat 

 surface, the extremities are raised, forming a kind of canal. Ex. 

 Fissurella rosea. Locality, Guyana, &c. 



Fissurella roiea. 



y. Conical species with horizontal borders. 

 Locality, Mediterranean and Atlantic. 



Ex. Fissurella Greeca. 



Fitturella Oraca. 



The distribution and habits of the Fissurellida; are the same as those 

 of Patella. Like that genus, Fissurella is littoral, and has been found 

 at depths ranging from the surface to 25 fathoms. 



The following species are described as British by Messrs. Forbes 

 and Hanley : Fisiurella reticulata, Puncturelta Noachina, Emaryinula 

 reticulata, E. rosea, E. crassa. 



Genera, Emarginula and Parmophorus. Cuvier observes that the 

 EmaryinuUe have exactly the same structure as the Fissurella, with 

 this exception, that the former, instead of the aperture at the apex 

 of the shell, have in their mantle and shell a small slit or notch at 

 their anterior border, which opens into the branchial cavity. The 

 borders of the mantle envelop and cover a great portion of those 

 of the shell. 



The eyes are situated upon a tubercle at the external bases of the 

 conical tentacula. The edges of the foot are furnished with a row of 

 filaments. G. B. Sowerby observes that " the animal of the Fismrella 

 is very nearly related to that of Emarginula, as the shell is to the 

 Emaryinula itself ; the fissure in the anterior margin of the latter 

 serving for the same purposes as the perforation in the vertex of the 

 former. One difference however is peculiarly observable, which is that 

 in Emarginula the vertex is directed posteriorly, contrariwise to that 

 of Fissurella ; for Lamarck is mistaken in speaking of the notch or 

 fissure in the edge of Emarginula as posterior." Of Parmophorus 

 Cuvier says that, like the Emarginula;, its shell is covered for a consi- 

 derable portion by the turned-up edges of the mantle ; this shell he 

 describes as oblong, slightly conical, and without hole or notch. The 

 branchia; and the rest of the organs are the same as they are in the 

 two preceding genera. G. B. Sowerby thus writes upon this point 

 ( 'Genera of Shells ') : " Emaryinula is more nearly related to Fissw- 

 rella than to Patella, inasmuch as its branchiae are not external, and 

 the little fissure or notch in the anterior edge is only the termination 

 of a narrow canal, that serves the same purpose in this shell as the 

 perforation in the summit of Fissurella. It is observable that 

 Lamarck has placed Emaryinula next to Parmophorus, without 

 seeming to have remarked the very great resemblance of the animals 

 to each other; we have thought ourselves justified, both by the 

 characters of the shells and of the animals, in uniting them ; this may 

 be objected to perhaps on account of the great difference in general 

 form ; but we answer that there are some species of Lamarckian 

 Emarginula, one of which we have figured, which approach very 

 nearly to Blainville's Parmophorus in shape. Another objection may 

 raise from the apparent want of the anterior fissure in Parmophorus 



