1921] NATURAL SCIENCES OF PHILADELPHIA. 371 



C. imiseriale is an obesely conic shell. There is an infra-siitural 

 series of rather short axial folds, interrupted by a spiral depression 

 or concavity, the folds stronger below it. On the last whorl the 

 folds are smaller than on the penult. About every fourth or fifth 

 fold is stronger on the penult whorl. The surface is rather finely 

 striate spiralh', and on the last whorl there are several low cords 

 which are weakly tuberculate, and there is a variceal swelling op- 

 posite the aperture. The last half whorl is broken away. There is 

 a strong callous ridge at the posterior part of the inner lip, as in C. 

 obesum. As broken the single specimen (no. 2595) measures, length 

 23, diam. 11 mm. 



This form stands near C. obesum, but differs by the impression 

 below the suture and the coarser spirals of the last whorl. 



Cerithium obesum Gabb. Plate XXXIIl. flgs. 5. 6. 



Ci:rithium obesum Gabb, Trans. Amer. Philos. Soc, xv, 1873, p. 237. 



Gabb's description is somewhat elastic, drawn to cover several 

 forms which he included under obesum, but several phrases apply 

 to onl}' one specimen of the type lot: "Outer lip effuse, internally 

 thickened.. Length 1 inch, diameter .5 inch" ''expanded lip". 

 These phrases must have had in view the specimen shown in our 

 plate XXXIIl, figs. 5, 6, since this is the only one in the lot which 

 retains any part of the outer lip, and agrees in size. It measures 

 24 mm. long, 12.5 wide, aperture 11.8 mm. long. The last whorl 

 rises conspicuously in its last third. The last three whorls have 

 rounded tubercles below the suture, very small and weak on the 

 antepenult. The whole surface is covered with a fine, nearly even 

 spiral striation. Eight whorls are present, the apex being sHghtly 

 worn. The basal part of the lip is broken. 



Type no. 2596 A. N. S. P. ; some 13 immature or broken examples- 

 varying in tuberculation, are no. 2596 a. 



Cerithium obesum ventricosior n. var. Plate XXXIIl, figs. 9, 10, 11. 12, 

 Cerithiu.in uniseriale Guppy, not Sowerby. 

 The shell differs from C. obesum by the wider angle of the spire 

 and relatively large last whorl. This obese form is represented by 

 numerous examples, all having the last third or half of the last whorl 

 broken away. It seems to be what Guppy has figured as C. uniser- 

 iale Sowb."' 



" Quart. Jour. Geol. Soc. xxxii, pi. 29, fig. 4. Maury, Bull. Am. Pal., 29, p. 

 124, pi. 21, figs. 14, 15. 



