FROM THE TERTIARY OF VIRGINIA. 37 



This shell may be identical with the D. lyra, Conrad, but its ribs are entire and its 

 aperture is not dilated. It is also much smaller. 



D. APERTA, PL. 36. FIG. 75. 



D. testa rotundato-conicd, sub-clevatd, tcnui, sulcatd; spird brevi, obtusd; suturis linearibus; anfractibus trihts, convexis, 

 rapide crcscentibus; suhis longitudinalibus. minutis, irregularibus, pene obsoletis; anfractu ultimo sub-angulato; basi sub-sul- 

 catd, umbilico magno, lato, profundo; apertura ovato triangular!, Integra. 



Shell rounded-conical, somewhat elevated, thin, sulcate; spire short, obtuse; sutures linear; whorls three, convex, 

 rapidly increasing; sulci longitudinal, minute, irregular, almost obsolete; last whorl sub-angular; base slightly sulcate; 

 umbilicus large, wide, profound; mouth ovately triangular, entire. 



Length .05. Breadth .08 of an inch. 



Remarks. The longitudinal sulci are very variable. The apex is almost mamillate. 

 The whorls are very much separated from each other by their convexity and the size of 

 the umbilicus. 



This is the most elevated species of the genus that I have met with. 



D. NATICOIDES, PL. 36. FIG. 76. 



D. testa discoidca, crassissimd, Icni; spird planulatd; suturis linearibus; anfractibus tribus, convexis; anfractu ultimo 

 maxima, rotundato; basi lavi; umbilico parvo, minime profundo; apertura parvdj ovatd; labro superne valde incrassatd. 



Shell discoidal, very thick, smooth; spire flattened; sutures linear; whorls three, convex; last whorl very large, 

 rounded; base smooth; umbilicus small, shallow; mouth small, ovatej outer lip very much thickened above. 



Length .07. Breadth .12 of an inch. 



Remarks. The last whorl almost covers those of the spire. The surface seems some- 

 what roughened. The mouth is nearly round. 



In general outline, this shell bears a strong resemblance to some species of Natica. 

 In this it differs from all the Delphinulse I have met with. 



FAMILY TURBINLTLE. 



GENUS ROTELLA. 

 R. SUB-CONICA, PL. 36. FIG. 77. 



R. testa orbiculari, sub-depressd, crassd, l<evi; spird brevl, obtusd; suturis linearibus; anfractibus qualuor, planu- 

 latis; anfractu ultimo sub-angulato; basi leEvi; callo lato, media crasso; apertura ovato-quadratd; columelld curvatd. 



Shell orbicular, somewhat depressed, thick, smooth; spire short, obtuse; sutures linear; whorls four, flattened; 

 last whorl sub-angulate; base smooth; callus wide, thick in the middle; mouth ovately quadrate; columella curved. 



Length .05. Breadth .07 of an inch. 



Remarks. This little shell has no very striking characteristics, and yet cannot be con- 

 founded with any other of its congeners. It is unusually elevated for a Rotella. 



R. CARINATA, PL. 36. FIG. 78. 



R. testa lenticulari, valde depressd, lenuissimd. lavi, politd; spird brevissimd, sub-ovatd, oblusd; suturis minimi's, 

 linearibus; anfractibus tribus, convexis, superne planulatis; anfractu ultimo acute angulalo, carinato, basi l<evi, politd; 

 callo paruo; apertura transversd, ovali; columella latissimd, curtd. 



Shell lenticular, very much depressed, very thin, sjnooth, polished; spire very short, sub-ovate, obtuse; sutures 

 very small, linear; whorls three, convex, flattened above; last whorl acutely angulate, carinate; base smooth, po- 

 lished; callus small; mouth transverse, oval; columella very wide, short. 



Length .04. Breadth .11 of an inch. 



