AMMOSITES.J 



MUSEUM OF ANIMATED NATURE. 



187 



2353. — Lister's Goniatitb 



(Goniatites Listen). In this species the striae rise 

 into ridges on the inner edge of the whorls. 



2554. — The Spibohbal Goniatite 



(Goniatltes spirorbis). This species is remarkable 

 for the multitudinous inner whorls. 



2.555. — Gibson's Goniatitb 



(Gonwtites Gibsoni). In this species the striae are 

 divided as in many ammonites. 



We may now turn to the sutures of the goniatites, 

 which exhibit the most singular curves, flexures, and 

 zigzags. The following arrangement, and the ac- 

 companying figures, will show the principal varia- 

 tions in the sutures, which are very interesting, and 

 which may be compared with actual specimens by 

 those who possess them. The arrow in each case is 

 supposed to point towards the apertur.e. 



Division 1. The dorsal lobe simple, one lateral 



lobe. 



Lateral lobe single, and rounded; Fig. 2556, 

 Goniatites expansus. 



Lateral lobe single and angular; Fig. 2357, 

 Goniatites sublaevis. 



Division 2. Dorsal lobe simple, more than one 

 lateral lobe. 



Lateral lobes linguiform and nearly equal ; Fig. 

 2558, Goniatites Henslowi. 



Lateral lobes rounded and nearly equal ; Fig. 

 255f), Goniatites serpentinus. 



Inner lateral lobes veij much the largest ; Fig. 

 2.560, Goniatites Munsteri. 



Lateral lobes very unequal and oblique; Fig. 

 2561, Goniatites Haeninghausi. 



Division 3. Dorsal lobe divided ; lateral lobe 

 single. 



Lateral lobes and sinuses rounded; Fig. 2562, 

 Goniatites bidorsalis. 



Lateral lobes and sinuses angular; Fig. 2563, 

 Goniatites striatus. 



Division 4. Dorsal lobe divided or complicated ; 

 lateral lobes more than one. 



Lobes rounded or loop-like ; Fig. 2.564, Goniatites 

 cyclolobus. 



It may here be observed that the same transition 

 rocks which contain a large portion of the con- 

 tinental species of goniatites, yield also examples 

 of a cognate group, from which indeed they are 

 with difiSculty to be distinguished. These have re- 

 ceived the name of Clymenia ; and it has been 

 observed " that if the goniatites are considered as 

 of the ammonoid type, the clymenia may be re- 

 garded as of the nautiloid type." Their siphon is 

 always on the inner margin, and the septa, instead 

 of a reflex wave, on the dorsal line, have a bend 

 forward towards the aperture. The clymeniae have 

 all the variations of form and surface which obtain 

 among the goniatites. The following figures re- 

 present the variations of the suture in several 

 species : — 



Fig. 2565, Clymenia laevigata. 

 Fig. 2566, Clymenia corapressa. 

 Fig. 2.567, Clymenia planorbiformis. 

 Fig. 2iJ68, Clymenia striata. 

 Figs. 2569 and 2570 exhibit a comparison between 

 the suture of a species of ammonite, and one of an 

 allied group, termed Ceratites, supposed to be 

 peculiar to the muschelkalk. 

 Fig. 2.571, Ammonites planicostatus. 

 Fig. 2.572, Ceratites nodosus. 

 As other examples of the sutures of ammonites, 

 we may refer to the following : — 



Fig. 2573, Ammonites sublaevis, from Kelloway 

 rock. 



Fig. 2574, Ammonites venustus, from Speeton 

 clay. 



Fig. 2.575, Ammonites Walcotii, from the lias. 

 Another group of fossil shells, inhabited by 

 cephalopodous tenants, is termed Baculites. This 

 genus was first discovered by Faujas de St. Fond in 

 the limestone of Maestricht, and is found in the 

 limestone of Valognes, in Normandy, in considerable 

 abundance. The shell is straight, more or less com- 

 pressed, conical or rather tapering to a point, and 

 Tery much elongated. The chambers are sinuous 

 and pierced by a marginal siphon ; and the last 

 chamber is several inches in length. Fig. 2.570 

 represents the Baculitos vertebralis : a, b, portions 

 of the fossil shell, exhibiting the character of the 

 sutures ; c is a detached joint. 



Another fossil form of the ammonite group is 

 that termed Turrilites. In this genus the shell is 

 spiral, turreted, and chambered; the chambers are 

 divided by sinuous septa, the siphon piercing their 

 discs. The aperture is round. 



It would appear that the shells of this form 

 among the extinct cephalopods are all sinistrorsal, 

 and the septa have the sinuosities of the ammonites. 

 According to Mr. Sowerby, the siphuncle is situated 

 near the upper part of the whorls, and the cavity 

 Vol. II. 



beyond the last enclosed chamber is very large, so 

 that the shell was external and tenanted as in the 

 case of the nautilus. In our island specimens of this 

 genus occur in the chalk and green-sand ; and 

 similar strata on the continent also afford them. 

 Fig. 2577 represents an imperfect specimen of 

 Turrilites costatus. 



Another fossil group of shells, belonging to ex- 

 tinct cephalopods, are the Belemnites, Orthoceratites, 

 Cyrtoceratites, &c. The belemnites, which have 

 been termed arrow-heads, thunder-stones, &e., and 

 which have been also regarded by some as the 

 teeth of some unknown strange animal, and by 

 others as the spines of some species of echinus, to 

 say nothing of many vague conjectures besides, are 

 extremely abundant in the chalk formations, in the 

 lias, and the oolite. They are evidently internal shells 

 analogous to those of the sepia officinalis, but more 

 solid, and of a diff'erent figure, being long and 

 conical. M. de Blainville, in his memoir published 

 at Paris, in 1827, has separated the genus Belemnites 

 into many divisions according to the shape of the 

 shells, and has recorded a great many species. 



Professor Agassiz is of opinion that the fossil ink- 

 bags of cuttle-fish, found in the lias at Lyme Regis, 

 belonged to Belemnites, and the reasons upon 

 which he founds this conclusion are derived from 

 the fact that specimens of the belemnite have been 

 discovered presenting the ink-bag in situ. Fig. 

 2.578 represents Belemnites canaliculatus with a 

 portion removed, showing the internal chambered 

 part. Miller, in his paper in the ' Transactions of 

 the Geological Society,' gives the following as the 

 generic characters of the belemnites:— 



" A cephalopodous molluscous animal provided 

 with a fibrous spathose conical shell, divided by 

 transverse concave septa into separate cells or 

 chambers, and inserted into a solid, laminar, fibrous 

 spathose, subcorneal, or fusiform body, extending 

 beyond it, and forming a protecting guard or 

 sheath.'' To this may be added that it was internal 

 like the gladius of the calamary or the ' bone ' of 

 the cuttle-fish. 



To the Silurian rocks, the Devonian, and the car- 

 boniferous or mountain limestone systems of Europe 

 and North America, belong the fossil Orthoceratites. 

 The true orthoceratites are straight and conical in 

 form, with dissepiments or sutures approximate, 

 concave, oblique, with a slight wave in front, or in 

 that part of the shell where the siphuncle is situated. 

 The siphuncle is small, and placed between the 

 edge and centre of the septa or dissepiment. These 

 fossils in many places have been erroneously re- 

 garded as crocodiles' fails. The late Mr. Martin, 

 in his ' Petrificata Derbiensia,' who figures two 

 species from the black marble at Ashford, observes : 

 " The crocodile, said to have been found in the 

 limestone at Ashford, appears to be nothing more 

 than a particularly large specimen of this or some 

 other orthoceratite, probably the species we have 

 figured in the 38th plate ;" and he adds, " as a 

 further confirmation of the opinion we have formed 

 respecting this supposed crocodile, we have to 

 remark that the men who now work in the marble 

 quarries at Asford continue to call the orthocera- 

 tites, when they meet with them, crocodiles' tails, 

 agreeably to the idea which was first entertained on 

 finding these bodies." 



Fig. 2379 represents the Orthoceras laterale. 

 It has been remarked that " the cases are few in 

 which the apex of orthoceratites has been actually 

 observed;" and that " in several cases of supposed 

 straight shells the apical part is seen to be curved," 

 whence it is probable that the term orthoceras (opBos, 

 straight ; Kepas, a horn) is not universally or strictly 

 applicable. 



Among the numerous allied genera we may allude 

 to the following species :— 



Fig. 2580, Cyrtoceras depressum. 

 Fig. 2.581, Lituites articulatus. 

 Figs. 2582 and 2583, Phragmoceras ventricosum. 

 In classing the bent or partially convoluted 

 polythalamacea, we may find advantage in attend- 

 ing to the situation of the siphuncle. For example, 

 the siphuncle is subdorsal or approaches the outer 

 line of curvature in Cyrtoceras, Goldl'uss, and Gyro- 

 ceras, Meyer; it is subcentral in Lituites, Breyn ; 

 and it is subcentral or approaches the inner line of 

 curvature in the genus Phragmoceras, Broderip. 



The geological distribution of these forms is 

 nearly as in the orthocerata. They are all peculiar 

 to the strata below the new red system ; and mostly 

 occur below the carboniferous or mountain lime- 

 stone. Phragmoceras prevails in the Ludlow rocks ; 

 Cyrtoceras specially abounds in the strata of South 

 Devon, the Eifel, and the mountain limestone ; and 

 Gyroceras and Lituites fellow nearly the same 

 rule ; a few species of Lituites occur in the Silurian 

 rocks. 



The brief characters of the generic groups which 

 follow may be sufficient for the recognition of per- 

 fect specimens, but such are rarely found in the 

 older rocks, where aloneHhey occur. 



Cyrtoceras (Kvpros, curved, and xepas, a horn), 

 Goldfuss. Bent, arched, or partially convoluted, 

 the free end being sometimes elongated and straight. 

 Septal edges seldom free from a slight waving ; 

 siphuncle subdorsal, or even marginal, seldom quite 

 round ; aperture nearly orbicular. 



Example, Cyrtoceras depressum. From the 

 Eifel. 



Several other species occur in Devonshire, near 

 Ludlow, &c. 



Gyroceras (yvpcs, incurred ; xtpos, a horn), Meyer. 

 Coiled like a tendril, so that the volutions do not 

 touch. Septal edge even, siphuncle dorsal, mar- 

 ginal. Aperture nearly round. 



Gyroceras gracile, Meyer. Bronn, in ' Leth. 

 Geog.,' vol i., fig. 0. From the states of Dillen- 

 burg. 



Lituites, Breyn. Convoluted, so that the volu- 

 tions touch in all the inner part, but afterwards 

 extended into a straight or bent portion. Septa 

 pierced by a subcentral siphuncle. Aperture nearly 

 round. 



Example, Lituites articulatus. Sow. 



Phragmoceras (^ppay/ia, septum ; Kepas, a horn), 

 Broderip. Shell incurved and compressed, more 

 or less conical : septal edges entire, crossed ex- 

 ternally by the lines of growth ; siphuncle near the 

 inner margin ; aperture contracted at the middle, 

 its outer extremity produced into an elongated 

 beak. 



Example, Phragmoceras ventricosum. Broderip, 

 in ' Silurian Researches.' 



Among the fossils derived from extinct species of 

 cephalopods, are those constituting the genus Bel- 

 optera, established by Deshayes, and described by 

 M. de Blainville as belonging to a form entirely 

 unknown, but which was characterized by contain- 

 ing on the back part of its muscular envelop a 

 symmetrical calcareous or bony shell, formed of a 

 thick solid .summit very much loaded behind, and a 

 front tube more or less complete, the cavity of 

 which is conical and annular, the shell or bone 

 having wing-shaped appendages without any an- 

 terior shield-like prolongation. 



De Blainville divides the genus into two sections. 

 The first consists of species whose wing-shaped 

 appendages are united below the summit, and whose 

 cavity is somewhat in the shape of a scuttle (hotte) ; 

 of this section Beloptera sepioidea is an example. 

 (Fig. 2584.) 



The second includes species whose wing-shaped 

 appendages are distinct, and whose cavity is com- 

 pletely conical, with traces of chambers and of a 

 siphon. Of this division Beloptera belemnoidea is 

 an illustration. (Fig. 2385.) 



De Blainville observes that this genus ought to 

 be placed at the end of the sepiacea, or cuttles ; 

 and that the first of the species is evidently very 

 much allied to the bones of those animals, while the 

 second approaches to the belemnites. 



After all, the probability is that these bodies are 

 only portions of the bones of some of the cuttle- 

 fishes ; and this appears to have been the opinion 

 of Cuvier. 



If a perfect bone of the common species of our 

 coasts be closely examined, a structure very analo- 

 gous to the conical circularly-grooved cavity of 

 Beloptera, although in a more expanded form, will 

 be observed. These fossils have been found in the 

 London clay, and other beds above the chalk. 



Voltz, in his memoir on Belemnites, makes Bel- 

 optera sepioidea a distinct genus under the name 

 ofBelosaepia. 



CLASS PTEROPODA 



(Pteropods, as Clio, Hyalsea, &c.). The 

 Pteropoda, or wing-footed mollusks, are so called 

 because they are constructed for moving through 

 the waters, of which they are the tenants, by 

 means of expanded fin-like membranes, placed 

 on each side of the head ; some, as the Clio, so 

 abundant in the northern seas, are covered with a 

 contractile envelop, but are otherwise naked and 

 destitute of a mantle. Others, as the Hyalaea, 

 Spiratella, and Cleodora, have a mantle protected by 

 a shell ; all are bise.xual. 



2586.— The Polak Clio 



(Clio borealis). The Clio borealis may be de- 

 scribed as a sort of marine slug with a pair of wing- 

 like fins or oars attached to each side of the neck, 

 by means of which the animal rows itself merrily 

 along, and sports amidst the watei-s of the Polar 

 Sea, rising and descending at pleasure. 



These oars are made up of muscular fibres, wtncti 

 pass through the neck from one expanded appen- 

 dage to the other, so that the organ is m fact single, 

 and may be compared to the double paddled oar 

 with which the Greenlander propels and steers his 



