INSTITUTE OF SCIENCE, PHILADELPHIA. 289 



Potamides (Pyrazisinus) scalatus Heilprin. 

 Plate 15. figures i, 4, 7, 8, 10 b. 



Cerithidea scalata Heilprin, Trans. Wagn. Inst. i. p. 132, pi. 16 b, fig. 71, 18S7. 



Pliocene of the Caloosahatchie beds, Myakka River and Shell Creek, 

 Florida, Willcox and Dall ; also off Stump Pass, thrown up on the beach by 

 the sea from submarine Pliocene beds. 



In the typical form (fig. i) the transverse ribbing is strong and the spiral 

 grooving is faint or absent behind the ribs; the varix is less prominent than 

 in P. cornutus and P. canipanulaUis. The way in which the lower lip grows 

 round so as finally to enclose the canal is shown in figures 7 and 8. The 

 posterior end of the outer lip is extended backward and grooved sometimes, 

 as in P. campa7itilahis , though not shown in the specimen figured. In the 

 variety ecarinatus (fig. 4) the transverse sculpture is absent or reduced to faint 

 ripples, as in many specimens of P. campajiulatiis, the varix is feeble, and the 

 spiral grooving continuous back to the suture. 



The appearance of these three forms suggests that with sufficient material 

 they might be so connected as to form merely subordinate races of one 

 species. The differences observed are not greater than exist among Cerites 

 now living which are obviously of one and the same species and, perhaps, 

 progeny of one pair of specimens. 



Potamides (Pyrazisinus) acutus n. s. 

 Plate 22, figure 19. 



Older Miocene of the Tampa limestone on the Hillsborough River above 

 Tampa, Florida, Dall. 



Shell stout, with an acute spire and ten or more convex whorls ; suture 

 distinct, not deep; nuclear whorls about three in number, smooth, subsequent 

 whorls finely spirally striate ; transverse sculpture of twelve or more little- 

 elevated, sharpish ribs with much wider interspaces, most prominent near the 

 periphery and obsolete toward the sutures ; lines of growth flexuous, not 

 prominent; last half of the last whorl beginning with a strong varix ; aperture 

 large, pillar short, stout, outer lip exhibiting a prominent callosity where it is 

 attached to the body, then receding, then patulous and projecting in front, 

 then sweeping round much prolonged until it touches or nearly touches the 

 varix ; inside of the lip smooth or obscurely striated. Alt. 40; max. diam. 

 about 23 mm. 



This remarkable form occurred as a mold in the soft limestone of the 

 Hillsborough River. By sacrificing this mold a tolerable cast of the shell in 

 gutta-percha was secured, from which the drawing was prepared. It is readily 

 distinguished from the other species of this group by its acute spire and the 

 prolonged sweep of the outer lip. 



