270 APPENDIX. 



frosted on the central line, not irregularly setose on the edges, 

 but most elegantly clothed, each on both sides, with twelve to 

 fourteen long hyaline cilia, arranged in symmetrical series, in- 

 clining obliquely from base to point, and diminishing in length 

 in like manner. The eyes are very large, black, and lateral, 

 attached nearly at the external bases on round inflations to the 

 main stems, there being no distinct pedicles. No head-lobes were 

 detected. There are two neck-lappets of different form, the one 

 on the right side being narrowish, flat, and semiserrated ; that of 

 the other side shorter, suboval, and plain. The foot is subtrun- 

 cate or rounded in front, superficially labiated, forming at the 

 angles long curved linear auricles ; it is moderately long, and 

 rather obtuse behind. The operculigerous lobe is plain ; it 

 carries, near the extremity, a circular corneous close-set spiral 

 operculum of from six to eight turns, and on each side, at equal 

 distances, three not very long nor slender flattish tentacular fila- 

 ments. The genitale springs under the right tentacle ; it is flat- 

 pointed, and lies horizontally, nearly extended to outside the 

 aperture, not reflected in the branchial vault. The excretory 

 canal is a short pendant cylinder on the right side, just above the 

 first vibraculum." Mr. Clark's observations, of which the above 

 is an abstract, were made on individuals taken in the coralline 

 zone, in fifteen fathoms water, off Budleigh Salterton. He re- 

 marks that it is an active and not shy creature. 



Vol. iii. p. 1G4, SkeneaI Cutleriana. 



Plate CXXXII. fig. 4, 5. 



We are enabled to amend our description of this shell from 

 additional specimens having been forwarded to us by the author 

 of the species. Our surmise, that it was no Skenea is confirmed; 

 it belongs rather to the section Margarita of the genus 

 Trochus. 



The shape is not orbicular (as we erroneously stated), but 

 obliquely subglobose, and the whitish surface is slightly tinged 

 sometimes with orange, sometimes with pink, in the recent ex- 

 amples. The shell is ordinarily a little iridescent towards the 

 mouth, and on the upper whorls so far translucent that the 



