INSTITUTE OF SCIENCE, PHILADELPHIA. 287 



drawn from a gutta-pircha cast of the original mold. It has so far only 

 been found in the shape of molds in the lime rock. The new figure is suf- 

 ficiently clear, and it need only be added that all the specimens examined 

 appear to have been decollated in life. The tubercles on the posterior spiral 

 are sometimes very prominent, almost spinose, and the other spirals may all 

 be tuberculous. Toward the aperture they become more prominent than on 

 any other part of the shell, contrary to the usual rule. The base is discoid, 

 with three small spiral, elevated lines. The canal is deep and truncate, the 

 suture sometimes channelled and sometimes appressed. The length of the 

 type-specimen is 31 and its breadth 15 mm. 



Subgenus Lainpanella Morch. 

 Potamides (Lampanella) transecta Dall. 

 Plate II, figure 7. 

 Potamides ^Lampanella) transecta Dall, Trans. Wagn. Inst. iii. p. 189, pi. 11, fig. 7, 1890. 



Older Miocene of the Orthaulax bed at Ballast Point, Tampa Bay, 

 Florida. 



Shell with an extremely acute tip, which is usually lost, two or three 

 minute, smooth nuclear whorls and about twelve subsequent sharply sculpt- 

 ured whorls ; spiral sculpture, between the distinct but not channelled 

 sutures, of four sub-equal strap-like spirals separated by nearly equal chan- 

 nelled interspaces, overriding seventeen or eighteen narrow, rounded, some- 

 what flexuous transverse riblets which cross the whorls ; the intersections are 

 prominent, but not nodulous, the base is similarly sculptured without riblets ; 

 on the later whorls smaller intercalary spiral lines begin to appear ; there is 

 a single varix at the end of the first half of the last whorl, but it is not very 

 prominent ; the pillar is short and simple, the canal truncate, well defined ; the 

 outer lip is slightly thickened, expanded and internally grooved in harmony 

 with the sculpture ; the body has a small subsutural ridge and a thin, reflected 

 callus. Lon. of figured specimen 17.5 ; max. diam. 8.5 mm. 



This neat little species seems not uncommon in the silex-beds. 



Other species of Potamides in our Tertiary are the Eocene P. alabami- 

 ensis Whitfield, from Bell's Landing, Alabama, and P. {Cerithium) totnbig- 

 beensis Aldrich, from Wood's Bluff, of which I have examined typical speci- 

 mens. 



Subgenus Pyrazisinus Heilprin. 

 Pyrazisinus Hp., Trans. Wagner Inst. i. p. 115, 1887. 



This group is intermediate between Cerithidea and Potamides. In its 

 effuse thickened outer lip with a wide posterior sinus it resembles the former 

 and also Pyrazus ebenimis, but in its truncate large canal it recalls Potamides. 

 -The habit of the shell is like that of some Ceritliideas, yet some of the species of 

 Potamides are also similar. In short, this is one of the links constantly turn- 



