INVERTEBRATE PALEONTOLOGY. 369 



believe that such shells can be properly included in Papa, as typified by forms 

 like R. papyracea, Lamarck, with their thin shell, round non-carinate body- 

 volution, deep suture, nearly hidden spire, and strongly internally-sulcated 

 outer lip. Mr. Conrad, however, as elsewhere stated, has expressed the 

 opinion that these Indian species (see Am. Jour. Conch., IV, 248) belong to 

 his genus Pyrifusus. To me, however, they certainly appear much more 

 nearly related to his Pyropsis, in almost every respect, than to the type of 

 Pyrifusus, or to the forms' I have here referred to that genus. 



Both Mr. Gabb and Mr. Conrad (to whom I sent plate 31, with the 

 figures of the shells I here refer to Pyropsis) express the opinion that they 

 are distinct from that genus, and really belong to a new genus. They seem 

 to think that these forms are distinct from Pyropsis in their twisted canal and 

 less prominent fold on the columella ; the canal of the type of Pyropsis being 

 by them viewed as perfectly straight. I should remark, however, that their 

 opinion in regard to our type was formed entirely from the figures on 

 plate 31, and without seeing the cut of Pyropsis Bairdi, var. rotula, given on 

 a following page, showing the inner lip partly broken away. In this, it will 

 be seen that the partial breaking-away of the inner lip gives it much the 

 appearance of that of the type of Pyropsis, and shows that the colu- 

 mella, is quite straight above; the twist and umbilical ridge being only 

 formed below, so as to be broken away in Mr. Conrad's type of Pyropsis. I am 

 therefore much inclined to think that there is really less difference in these 

 shells than they have been led to think Nevertheless, as they are both 

 familiar with the type of Pyropsis, which I only know from the published 

 figure and description, it is still possible that they may be right ; in which 

 case I would at least propose subgenerically for our type, the name Apiotropis, 

 which, if retained, would require the name of the following species to be 

 written Pyropsis {Apiotropis) Bairdi. 



This genus, as here understood, seems to be mainly, if not entirely, 

 confined to the Cretaceous rocks; though possibly a few Tertiary forms may 

 belong to a section of the same group. 



Pyropsis Bairdi, M, & H. (sp.). 



Plate 31, figs. 10, a, 1>. 



Pyrula Bairdi, Meek and Hayden (185fi), Proceed. Acad. Nat Sci. Philad., VIII, 66. 

 Busycon Bairdi, Meek aud Hayden (1856), ib., 126. 



Tudicla (Pi/rojisis) Bairdi, Meek (1864), Smithsonian Cheek-List N. Am. Cret. Fossils, 2'.i. 

 Compare Pyrula Biehardsoni, Tnomey (1855), Proceed. Acad. Nat. Sci. Philad., VII, 169. 



Shell attaining a large size, distinctly pyriform ; spire depressed to less 

 47 h 



