106 



Section BROCCHTA, Bronn, 1827. 



Irregularly conical, apex slightly spiral, directed to the left ; 

 left margin with a profound sinus, its posterior half folded. 

 Tertiary, 2 sp. C. sinuosa, Bronn (S. and S. Conch., t. Ixiv, f. 

 80). A single living species is mentioned but not described as 

 G. reductus, Desh., Isle of Bourbon. 



Section THYCA, H. and A. Adams, 1854. 



Shell conical, longitudinally grooved, transparent, slightly 

 curved. Indian Ocean, a single species on Asteria. 



Subgenus METOPTOMA, Phillips, 1836. 



Shell depressed, conical, elliptical, truncated behind, apex not 

 spiral, posterior, slightly inclined posteriorly. Carboniferous, 

 Europe, United States. C. Solaris, Kon. (S. and S. Conch., t. 

 Ixxxiv, f. 52). 



In the above-named work I included this among the sections 

 of Patella, which it resembles exteriorly ; the muscular im- 

 pression is like that of Capulus. Tryblidium, Lindstrdm, 

 1880, is a synonym. 



[Subgenus SPIRICELLA, Rang., 1828. 



Shell flattened, elongated, with a sinistrally situated apex, 

 and a corresponding cavity in the interior ; muscular impression 

 very indistinct. 



C. unguiculus, Rang. (S. and S. Conch., t. Ixv, f. 96, 97). 

 Miocene, France. 



The relations of this group are obscure ; it may belong near 

 Umbrella.] 



Genus AMATHINA, Gray, 1842. 



Shell depressed, oblong ; apex posterior, not spiral, with 

 three strong ribs radiating from it to the anterior margin which 

 is produced into three points. 



Animal with elongated head, the eyes sessile on the margin 

 behind the short tentacles ; mantle margin entire, a tentacular 

 median filament at the hind part. Indian Ocean. 



Genus PLATYCERAS, Conrad, 1840. 



Shell depressed subglobose, subovoid or obliquety subconical ; 

 spire small ; volutions few, sometimes free and sometimes con- 



