264 PROCEEDINGS OF THE NATIOXAL MUSEUIM vol. 85 



The type, U.S.N3I. no. 468739, comes from the large mogote at 

 Cayo San Felipe. It is a perfect specimen having 6.8 whorls and 

 measures : Length, 24.8 mm ; greater diameter, 14.4 mm ; lesser diam- 

 eter, 10.7 mm. 



The animal of this species is ash-gray, with the tentacles coral- 

 red, their base being a little paler, gradually passing into flesh-color 

 at their origin. Snout flesh-color at tip. Sole of foot flesh-color 

 with smoky suffusion. Foot medially longitudinally cleft; motion 

 of the two sides alternate. 



This species resembles certain forms of Chondrothyretes {Chondro- 

 thyretes) reticidata, but the absence of a definite cut in the inner lip 

 of the outer peristome and open umbilicus easily mark its distinction. 



CHONDROTHYRA (PLICATHYRA) CRASSA, new species 



Plate 15, Figure 3 



Shell large (early whorls unknown) ; peristome double, the inner 

 slightly exserted, somewhat expanded; the outer strongly expanded 

 and radiately fluted, the inner lip broader than the outer and adnate 

 to the preceding whorl. The color varies from unicolor yellowish 

 white to dark chestnut-brown, or it may be spirally banded or inter- 

 ruptedly so ; in the latter case there is usually an axial arrangement 

 of spots as well as a spiral. Operculum typically cliondropomoid. 



The type, U.S.N.M. no. 367848, has 3.2 whorls remaining and 

 measures: Length, 31.9 mm; greater diameter, 22.0 mm; lesser diam- 

 eter, 16.0 mm. 



This species comes from the high summits of the Sierra San Carlos 

 between Luiz Lazo and Sumidero. Its large size will readily distin- 

 guish it from C. (P.) uniplicata, its nearest ally. 



CHONDROTHYRA (PLICATHYRA) WRIGHTI, new species 



Plate 16, Figure S 



Shell rather large, thin, of pale-yellow ground color with numerous 

 interrupted spiral bands of brown, which are also arranged in axial 

 series. These bands are present on both spire and base. The axial 

 arrangement is slightly retractive. The early whorls are decollated 

 in the unique type. Suture feebly denticulated by the axial riblets 

 but well constricted. Periphery strongly rounded. Base moderately 

 long, well rounded. The remaining whorls are slightly inflated, well 

 rounded, and marked by fine, retractively slanting, closely spaced, 

 axial threads, which are about half as wide as the spaces that sep- 

 arate them, and spiral lirations, which are slightly stronger than the 

 axial threads and a little more distantly spaced. The junction of 

 these two elements forms weak nodules, while the spaces enclosed 



