180 



CHAPTER XXX. 



CANCELLAKIA WANTING IN THE BRITISH FAUNA. — TRICHOTROPIS. — CERI- 

 IHOPSIS, ITS CHARACTER AND HABITS. 



CANCELIiABIAD.^. 



Of tlie genus Cancellana itself^ with its elegantly-formed 

 and well-sculptured shells^ our own shores do not present a 

 single example. The nearest approach to it is found in a 

 rather small boreal mollusc^ named 



I. Trichotropis horeaUs, — It has a neat little fusiform 

 shelly with spiral keels, covered by an epidermis, which, 

 Avhen in good condition and not too aged, is gathered up, at 

 the upper keel, into a coronet of stiffish hairs. The aper- 

 ture is pointed in front, ending in a slightly-depressed canal. 

 Behind the inner lip is a broad hollow^, or umbilicus. 



The head of the animal is short and broad, having a retrac- 

 tile proboscis, and two pointed tentacles, with the lower 



