PATELLTD^. 117 



C. niher : with valves smooth, shining, red; border very 

 finely powdered. 



C. cinereus : mottled with various colours ; valves and bor- 

 der finely and irregularly granulated. The commonest 

 species. It is generally dull, frequently ashy, and the 

 granulations are only seen on close examination. 



C. alius : very difficult to distinguish from C. cinereus j the 

 scales of the border are coarser in proportion to those 

 of the valves. 



C. asellus : broad and depressed, of a dull ash-colour ; gra- 

 nules on the middle areas in rows ; border narrow. 



C. cancellatus: smaller, narrower, and more elevated and 

 rounded than C, asellus. 



C. lavis : beautifully marked with red, rather flat but angu- 

 lar ; valves smooth, border finely reticulated. 



C. marmoreus : mottled ; valves microscopically granulated, 

 border quite plain. 



PATELLID^. 



In the Chitons we found something like a distinct head 

 and mouth, with toothed tongue, but no tentacula and no 

 eyes. The Tatellidm however are not all in the dark; some 

 of them have eyes, and all of them have tentacula. They 



