242 VOLVULA-SCAPHANDRID^. 



Alt, 0-074 in. diam. 0*034. Mouth, breadth at same place, 0'005 

 inch. ( Wats.). 



Torres Strait, 3-11 fms. 



Cylichna (Volvula) sulcata WATS., Ch'all., Kep. Gastr., p. 670, pi. 

 50, f. 6. 



In form this somewhat resembles Volvula angustata A. Adams, 

 but the sculpture is quite different. Compared to Cylichna acum- 

 inata A. Adams, the apex of the Challenger species is not spike-like 

 and the spiral striae are stronger. ( Wats.). 



i 

 Family SCAPHANDRID^E Fischer. 



Shell spiral, external, the spire sunken or concealed. Animal 

 with a short subquadrate foot, truncated or forked behind ; frontal 

 disc without tentacles, the posterior lobes obsolete ; epipodial lobes 

 well developed. Radula having the central tooth small, with a very 

 large lateral on each side of it, and either a few smaller uncini or 

 none. Gizzard containing three calcareous plates, which are not 

 tuberculate. 



This family differs from Tornatinidcz in the obsolescence of posterior 

 lobes on the head-shield, in the well-developed radula, and the large 

 lateral epipodial lobes. It differs from Bullidce, in the highly 

 specialized form of the radula-teeth and their small number in a 

 transverse row. 



The form of the shell is so various in Scaphandridce that no useful 

 diagnosis of the family can be drawn from that organ. It would be 

 very difficult to indicate any means of distinguishing the shells of 

 some species of Cylichna from the genera Retusa and Haminea, 

 although the soft parts of these three genera are very different. As 

 in the case of Tornatinidce, the present monograph does not pretend 

 to be a sufficient account of all the species, much less to decide 

 authoritatively questions of synonymy. In the present state of con- 

 chology, all systematic work on Tectibranchs is of a tentative and 

 superficial character; and if the following account serves the tem- 

 porary purpose of bringing together all of the described forms and 

 their literature, the object of the writer will be attained. It remains 

 for those who have opportunity to observe living examples to prop- 

 erly classify many of the species. 



