TROCHUS. 315 



as the sole, though diminished to he within its margins ; it 

 carries near the extremity the circular, corneous, moderately 

 close- set, spiral operculum of 6-8 turns, and on each side, at 

 equal distances, three, not very long nor slender, flattish ten- 

 tacular filaments issuing from tubercles of the same elegant 

 structure as the capitular ones ; these are not "vibrated with 

 the usual activity of the tribe, but the curved auricles of 

 the foot may be said to be "Isete vibrantes." The verge 

 springs under the right tentaculum; it is flat, pointed, and 

 lies horizontally, nearly extending to outside the aperture, 

 not reflected in the branchial vault. The canal of depuration 

 is visible at the right side just above the first vibraculum ; it 

 is a short pendent shoot or cylinder. 



This animal inhabits the coralline zone in fifteen fathoms 

 water, five miles off Budleigh Salterton ; it is active, marches 

 with quickness, not at all shy, and gave me good opportunities 

 of observing its peculiarities. 



It thus appears that the principal differences between this 

 species and its congeners are the mere specialties of the want 

 of distinct eye-pedicles, and the long linear curved auricles of 

 the foot. Axis Jj, diameter ^ uncise. 



This very important discovery of a desideratum that has 

 hitherto escaped detection, proves that the animal is nearly a 

 strict Trochus, which does not in the specialties show a greater 

 departure from the Trochidan type than is often seen amongst 

 the most classic species. This fact determines the fate of the 

 genus Skenea : its provisional members, the S. Cutleriana and 

 S. nitens of Philippi, called by some authors " Trochus pu- 

 sillus," are in all probability Trochi ; but I will not venture 

 to say as much of S. nitidissima. The S. lavis is scarcely a 

 variety of our present species. 



T. CUTLERIANUS, Clark. 



? Skenea Cutleriana, Brit. Moll. iii. p. 164, pi. 88. f. 3, 4 ; iv. p. 2/0, 



pi. 132. f. 4, 5. 

 ? S. costulata, Brit. Moll. iii. p. 167; iv. p. 271. pi. 132. f. 1,2,3. 



T. testa suborbiculari, albida, aliquantulum producta, anfractibus 

 tribus spiraliter exaratis ; striis subtilibus, undatis, transversis, 



