TROCHUS. 533 



The aperture is nacreous, nearly circular, large, and 

 more or less expanded ; in height it rather exceeds one- 

 half of the entire length of the shell ; in breadth it occupies 

 at least one-half the basal diameter. The outer lip is 

 simple, acute, and recedes considerably in front ; the pillar- 

 lip is narrow, thin, arched, and erect, only folding back 

 very slightly at the umbilical cavity. The breadth of the 

 shell, which is superior to its length, is about the sixth of 

 an inch. 



The animal — for drawings of which we are indebted to 

 Mr. Alder and Mr. Hancock — is of an orange colour, 

 mingled with dusky. The muzzle appears to be very 

 short, crenated, and deeply tinged on the summit with 

 dusky. The tentacula are short in proportion to the 

 body, rather stout, strongly ciliated. The head-lobes 

 seem to be obsolete. The eye-peduncles are short. The 

 neck-lappets are small, and even-edged. There are about 

 five rather dusky lateral cirrhi on each side, three placed 

 on the opercular region, and two anteriorly. The foot is 

 rather large, oblong, obtuse in front and behind, tinged 

 with dusky at the sides. The jaws are studded with 

 closely-set papillae. Each row of teeth on the lingual 

 riband (according to the drawing by Mr. Alder) consists 

 of a central denticle, which is rather broad anteriorly, 

 strongly hooked, and wide-necked ; flanked on each side 

 by six rather obtusely and broadly hooked laterals, and a 

 great number of narrow accessorials. 



This little shell ranges along the northern shores of 

 Britain on both sides, and is a littoral species, occasionally 

 descending into the Laminarian zone. It is usually found 

 amon? sea- weeds and under stones near low- water mark. 

 Tt ranges from Yorkshire and Northumberland (Alder) ; 

 northwards on the eastern coast (Bean) ; occurring in 



