176 COCHLOSTYLA-ORUSTIA. 



Subsection 2. ORUSTIA Morch, 1852. 



Orustia MORCH, Catal. Yoldi, p. 15 (in part ; first species H. 

 monticula Sow.). SEMPER (group of Cochlostyla), Reis. Phil. Laud- 

 moll, p. 196. 



Shell imperforate, turbinate-globose, rather thin, green under a 

 hydrophanous yellow cuticle, the base green. Lip thin, narrowly 

 reflexed ; columella vertical, deeply entering ; the umbilico-colu- 

 mellar tract notably concave, covered with a white callus. Surface 

 wholly free from spiral sculpture. 



Anatomy as in Cochlostyla generally. 



The entire absence of spiral sculpture and the presence of hy- 

 drophanous cuticle are the more important characters of the sub- 

 trochiform, thin-lipped species to which the name Orustia is restricted 

 by recent authorities. 



C. MONTICULA Sowerby. PI. 39, figs. 94, 95, 96. 



Imperforate, globose turbinate, rather thin, lightly obliquely stri- 

 atulate. Upper surface rich yellow and cream-colored, fading into 

 white on the earlier whorls through loss of the cuticle ; periphery 

 girdled by a dark brown band, below which is a wider yellow band ; 

 base bright green. 



There is no trace of spiral sculpture. The hydrophanous cuticle 

 is rich yellow, sometimes almost orange, on the last whorl, 

 becoming lighter above, and lost by erosion on the earlier whorls. 

 The dark girdle at the circumference is constant throughout the 

 large series which I have examined. There are 5 slightly convex 

 whorls, the last not deflexed in front, not angled at the periphery, 

 although the base is rather flattened. The apex is quite obtuse. 

 Aperture oblique, half-round, white within, faintly showing the brown 

 band. The lip is very narrowly subreflexed, white; columella sub- 

 vertical, deeply inserted, dilated over the umbilico-columellar tract 

 in a white concave callus, somewhat as in C. (Chromatosphwra) 

 aurata. 



Alt. 20, greater diam. 19 mill. 



Alt. 14J, greater diam. 16 mill. 



H. monticula SOWERBY, P. Z. S. 1840, p. 167. PFR., Monogr. i, 

 p. 226; Conchyl. Cab. t. 51, f. 13-17. RVK, f. 103. Cochlostyla 

 (Orustia) monticula SEMPER, /. c., p. 197, t. 8, f. 6 ; t. 13, f . 1 ; t. 

 18, f. 23 (anatomy). 



