FROM THE TERTIARY OF VIRGINIA. 263 



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-conicdj sub-elevatd, tenui, sulcald; spird brevi, obtusd; suturis linearibus; anfractibus tribus, convexis, 

 rapide crescentibus; sulcis longitudinalibus, minutis, irregularibus, pene obsoletis; anfractu ultimo sub-angulato; basi sub-sul- 

 catd, umbilico magno, lato, profundo; aperturd ovato triangular!, integrd. 



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 discoided, crassissimd, Icevi; spird planulatd; suturis linearibus; anfractibus tribus, convexis; anfractu ultimo 

 maxima, rotundato; basi Iczvi; umbilico parvo, minime profundo; aperturd parvd, 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, ovate; 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 Delphinula3 I have met with. 



FAMILY TURBINID^E. 



GENUS ROTELLA. 

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



R. testa orbiculari, sub-depressd, crassd, Icevi; spird brevi, obtusd; suturis linearibus; anfractibus quatuor, planu- 

 latis; anfractu ultimo sub-angulato; basi l<evi; callo lato, media crasso; aperturd ovato-quadrata; columella 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, tenuissimd^ Icevi, polita; spird brevissimd, sub-ovatd, obtusd; suturis minimis, 

 linearibus; anfractibus tribus, convexis, superne planulatis; anfractu ultimo acute angulato, carinato, basi Icevi, polita; 

 callo parvo; aperturd transversd, ovali; columella latissimd, curtd. 



Shell lenticular, very much depressed, very thin, smooth, 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. 



