INVERTEBRATE PALEONTOLOGY. 345 



;iiid to agree so much more nearly with another genus, Pyropsis, proposed by 

 him, that, if left to form a conclusion from the published figures and descrip- 

 tions alone. T should have l>een more inclined to refer these Indian shells to 

 the latter genus, than to the genus Pyrifusus. At any rate, they seem to differ 

 from Mr. Conrad's figure of the typical species of Pyrifusus, and to agree 

 much more nearly with that of Pyropsis, not only in form, but in having the 

 inner lip raised so as to form a more or less prominent- fold or ridge nearly 

 opposite the base of the aperture, while they both show a kind of posterior 

 notch at the top of the aperture, more nearly corresponding to the figure 

 of the type, of Pyropsis than to that of -Pyrifusus. Again, the Indian shells 

 have an umbilicated or perforated axis, with an obliquely-ascending, spiral, 

 umbilical ridge, or fasciole; while, in the type of Pyrifusus as figured, nothing 

 of this kind is seen. I am fully aware, however, that the presence or absence 

 of an umbilicus, or perforation of the axis, cannot always be relied upon as a 

 generic, or sometimes even as a specific, character. Yet it is certainly the 

 case that in some groups this character never occurs, while in others it nearly 

 always exists; and in genera having the general aspect of those under con- 

 sideration, with the perforation of the axis usually present, but sometimes 

 wanting, we almost always see, in the latter cases, the umbilical ridge still 

 remaining. 



It therefore certainly seems to me, that, if the Indian species mentioned 

 belong to Pyrifusus, the shells here referred to that genus under the sub- 

 generic name Neptuvella, should be viewed rather as forming a distinct genus 

 than a subgenus under that group. 



In general appearance, some of the species of the group Neptune/la 

 resemble certain recent forms, such as Fususl dilatatus, Quoy and Gaimard, 

 referred by H. and A. Adams to the genus Neptunea, Bolten. Yet they differ 

 from the recent typical forms of the latter genus, such as Fusus antiquus, 

 Lamarck, in being thicker shells, with more angular volutions, and in wanting 

 a papillary apex, as well as in having a solid axis, a straight canal, and no 

 umbilical ridge. 



The classification of all such forms was, until recently, "made easy" by 

 referring them indiscriminately to that common receptacle of all sorts of 

 fusiform shells — the genus Fusus. They certainly, however, seem to differ 

 from that genus as typified by such forms as Fusus colus. 



So far as yet known, the genus Pyrifusus, as here understood, appears 



to be mainly, if not entirely, confined to the Cretaceous rocks. 

 U u 



