308 BRITISH PALAXOZOIC FOSSILS. | CepHALOpopA. 
There can be no doubt that the characteristic band, and its accompanying sinus at the edge of the aper- 
ture, lodged the funnel of the cuttlefish (as in Argonauta); but I think the great thickness of the calcareous 
shell, and beyond all the testaceous deposit (or inner lip) formed on the inrolled part of the spire, like the black 
mark on the recent Nautilus, formed as in them by a reflected lobe of the back of the mantle, indicate that the 
shell was really attached to the animal, and therefore more like Nautilus than Argonauta. We have many 
examples of the embryonic appearance of the recent types being the permanent characteristic of the ancient 
fossil analogues ; and as the extremely young Vauwtilus is monothalamous, we only recognise an old law in placing 
Bellerophon in a new group; and as Prof. Owen and M. Valenciennes have demonstrated how little superior 
Nautilus is to the Pectinibranchiate Gasteropods in several points of anatomy, we would by this new position of 
Bellerophon dyvaw the connexion closer. The absence of chambers would confine these heavy shells constantly 
to the bottom like the Gasteropods, or like the occasional habit of Nautilus. 
Genus. BELLEROPHON (Moni/.) emend. by Defrance. 
Syn.— > (Bucania Hall. + Euphemus M°Coy). 
Gen. Char.—Shell thick, symmetrical, involute, globose, or discoidally coiled with the whorls exposed ; a 
sinus in the middle of the outer lip, from which a band extends backwards along the outer surface of the 
volutions ; inner lip thickened, expanded on the inrolled spire. 
The subgenus Bucania of Hall was proposed for the species with a wide umbilicus, but it seems im- 
possible to draw the line between these and the species with very small umbilicus or none. The subgenus 
Euphemus (M°Coy) was proposed (Carb. Foss. Irel.) in 1844 for the species supposed to want the band, and 
also supposed to have thinner shells than the others ; since then the group has been recognised and separately 
named by M. Barrande, and still more recently M. d’Orbigny has (in his Prodrome) also independently 
recognised the group, but confines to it Conrad’s name, Cyrfolites; but as I have recently ascertained that 
some of the types of this group (e.g. B. bilobatus, Ge.) have really got bands, when the external shell can be 
examined, and that in other, spirally sulcated, species, the band is merely obscured by the sculpturing, I think, 
contrary to my former opinion, and that of the above distinguished authorities, that the subgenus should again 
be merged into Bellerophon. As 1 have before remarked, the thickness and weight of the calcareous shells seems 
to me a decisive argument against the possibility of the Bellerophon belonging either to the Pteropoda or 
Heteropoda, when we consider the habits and the functions of the shell in these groups; the symmetry and 
completeness of their involution seems to me to separate them from any of the Gasteropodous genera to which 
they have been allied ; and on the whole there would be less objection to Professor Owen’s suggestion of placing 
them in the Octopodous group of Dibranchiate Cephalopods, close to Argonauta, than any other proposed 
arrangement, were it not for the distinct and often greatly thickened inner lip covering the part of the spire 
entering the aperture. No trace of this lip ever occurs in the Argonauts, which differ thus from all other involute 
shells, as well as in the mode of formation of their shell, which renders the occurrence of an inner lip impossible. 
As it is therefore clear that the shell of Bellerophon was secreted by the mantle, after the manner of Nautilus, 
1 have preferred viewing it as a monothalamous Nautilus, agreeing with embryo Nautili in this respect, and 
rendering more perfect the passage from the Tetrabranchiata to the Gasteropoda. 
BELLEROPHON BILOBATUS (So7.) 
Ref. and Syn.—Sil. Syst. t. 19. f. 13 =(B. elongatus + B. gibbus Port.) Geol. Rep. t. 29. f. 2 to 5. 
Sp. Ch.—Globose, involute ; sides and periphery very slightly flattened; mouth large, widely bilobed by a 
deep sinus, from which a wide flat band with arched strive extends (leaving no trace on the interior) ; umbilicus 
very small in the casts, closed in the perfect shell; surface marked with coarse, round, slightly irregular and 
flexuous close strize (seventeen or eighteen in one line), strongly arched from the umbilicus to the band, faintly 
decussated under the lens by very minute spiral strize, strongest at the umbilicus and sides of the band; casts 
90 
smooth ; diameter one inch two lines; proportional width of mouth %, depth of sinus 3. 
