COCHLOSTYLA-PTYCHOSTYLUS. 193 



I have not seen the typical CURTA (pi. 37, figs. 47, 48), which has 

 a light buff ground-color, the cuticle being pale above, brown below. 



The shell called B. dilatatus by Reeve has the ground-color almost 

 black, becoming rufous or yellow above, the lip dark-edged. 



The variety /? of Hidalgo, as well as the specimens before me, 

 one of which is shown in fig. 15, are the same as the form called B. 

 dilatatus by Reeve. While I am wholly disposed to consider these 

 shells the same as Pfeiffer's dilatatus, it should be mentioned that 

 Hidalgo has reached an opposite conclusion, from a study of 

 Pfeiffer's figures. The suite before me shows very great variations 

 in the degree of development of the columellar tooth, it being in 

 some examples scarcely noticeably truncated. 

 Var. PI. 60, fig. 16. 



Larger, more elevated, very solid ; black-brown below, rufous 

 above. Whorls 63 . Columellar tooth very strongly developed. 

 Alt. 40, diam. 28 mill. 



The specimen is denuded of cuticle. 



Var. DILATATUS Pfr. PL 60, figs. 13, 14. 



Chestnut-brown, tawny above, the last whorl having a white band 

 below the suture. 



B. dilatatm PFR., P. Z. S. 1846, p. 42 ; Conchyl. Cab. p. 110, t. 34, 

 f. 7, 8 ; Monogr. ii, p. 8. 



I am wholly inclined to consider this a mere variety of C. curia, 

 founded upon a specimen denuded of hydrophanous cuticle, except 

 for a band remaining below the suture on the last whorl. In case 

 my supposition is correct, the name dilatatus may be retained in a 

 varietal sense for all specimens of C. curta having a dark ground- 

 color, including Reeve's dilatatus. 



Section VIII. PTYCHOSTYLUS Mollendorff, 1888. 



Ptychostylus MLLDFF., Nachrichtsbl. D. M. Ges., 1888, p. 74. 

 Stylodonta (in part) of authors. Columplica (in part) HARTMANN, 

 Gasterop. Schweiz, p. 187, 188 (H. uniplicata the first species; see 

 under Stylodonta unidentata, this work, Vol. VI, p. 86). Not 

 Ptychostylis Gabb, a group of Trochidce. 



Shell globose-turbinate, formed of many closely coiled whorls, the 

 surface having hydrophanous cuticle ; aperture narrowly lunar ; 

 columella spirally twisted, having a strong tooth- like fold at the base. 



Animal externally like Cochlostyla. 

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