TROCHUS. 311 



appear a little imbricated, and each is marked by a raised line 

 or ridge ; they are microscopically striated across in a radiating 

 direction. L. 0-5. B. 0-55. 



Var. 1. electissima. Smaller and more regularly conical. 

 T. electissimus (Bean), Thorpe, Brit. Mar. Conch, p. 264. 



Var. 2. variegata. Also smaller, and ornamented by a few 

 short and broad dark reddish-brown rays on the npper part of 

 each whorl, besides the ordinary coloured streaks. 



Habitat : Abundant everywhere,, on stones and sea- 

 weed at low- water mark and in the laminarian zone. 

 Var. 1 inhabits deep water ; the other variety is found 

 in the Channel Isles^ as well as in the Mediterranean. 

 This species frequently occurs in our latest tertiary 

 strata^ including the Clyde, Belfast, and Sussex beds, 

 and the Red Crag ; Christiania, in lower and younger 

 deposits, 100-150 feet (Sars); Piedmont (Brocchi). 

 Living in Iceland (Mohr); Scandinavia (Linne and 

 others); Heligoland (Frey and Leuckart); North of 

 France (De Gerville and others); Vigo and the North 

 Spanish coast (M*^ Andrew); Mediterranean (Linne and 

 others); Adriatic (Chiereghini) ; Mogador (M' Andrew); 

 Black Sea (Krynicki and others). The bathymetrical 

 range given in these foreign localities extends from low- 

 water mark to 60 f. 



When crawling it moves each side of its foot by 

 turns. The left-hand pallial lappet serves for aerating 

 the sill, like the semitubular fold in the Muricidce and 

 other Siphonobranchiata. According to Loven the 

 eggs are yellowish and numerous, not enclosed in cap- 

 sules, but laid indiscriminately. M. Lespes detected 

 one of the Trematode parasites {Cercaria brachiura) in 

 the animal of this species at Arcachon. Its strong 

 shell does not protect it from also becoming the prey 

 of creatm-es larger than itself. Fishes devour it whole- 

 sale ; and Macgillivray tells us that on the shores of the 



