MALACOZOA. GASTEROPODA. TECTINIBRANCHIATA. 53 



or angulate, the columella arcuate, and often a little 

 projecting. Tpoxbs, a potter's wheel, or a top. Lin- 

 naeus. 



1. Trochus Sisyphmus. Shell imperforate, conical, 

 acuminate, with the turns flat, spirally grooved, each 

 with a prominent rim on the angle, the upper turns 

 granulate. Named, I suppose, from some fancied ana- 

 logy to the rolling stone of Sisyphus ; if so, it is erro- 

 neously written zizyphirws, 



2. Trochus conuloides. Shell imperforate, conical, 

 acute, with the turns flat, spirally grooved, with the 

 marginal ridge more prominent. Name from, its re- 

 semblance to a cone. 



3. Trochus Martini. Shell imperforate, conical, 

 acuminate, with the turns flat, with cord-like ridges, 

 the angular margin of the turns with a very prominent 

 crenulated rim. Named by Mr. Smith after Major 

 Martin. 



4. Trdchus cinerdrius, Shell umbilicate, depressedly 

 conical, convex, of five sulcato-striate turns, of a pale- 

 grey colour, with radiating, undulated, reddish purple 

 fines. Cinerdrius, ash-grey. 



5. Trochus tumidus. Shell umbilicate convexo-conical, 

 of five turns, which are depressed above, sloping, striate, 

 brownish white, with transverse waved dusky or purple 

 lines. Tumidus, swelled or bulging. 



GENUS 2. PHORCUS. Shell roundish, rather depressed, 

 thicki sh, with the turns convex, the aperture circular, 

 subangulate anteriorly ; the umbilicus deep. Phorcus, 

 according to Hesiod, a son of the sea and the earth. 

 Risso. 



1. Phdrcus Margarita. Shell roundish, rather de- 

 pressed, smooth, glossy, light-brown or olivaceous, with 

 the interior pearly. Margarita, a pearl. 



GENUS 3. SKENEA. Shell orbicular, discoid, with the 

 turns rounded, the aperture circular, the peristome com- 

 plete, the umbilicus wide. Named by Dr. Fleming after 

 Dr. Skene, an Aberdeen physician and naturalist. 

 E 2 



