COOKE : ON THE MACANDREW COLLECTION. 34 1 



will explain their absence. With the sole exception of Lepton 

 Clarkice, they may all be considered very rare, while in several 

 places their claim to a place in the list of British species rests only 

 a single discovered example. 



Pecten vitreus Chem. N. Hebrides. 



Lima Sarsii Loven. Shetland. 



L. elliptica Jeffr. Shetland and W. Scotland. 



Area obliqua Phil. Shetlands. Two valves only. 



Leda lucida Loven. N. of Hebrides. 



Limopsis boreal is Woodw, N. of Hebrides. One valve only. 



Montacuta tumidula Jeffr. Hebrides and Shetland. 



Lepton Clarkise Clark. 



Loripes divaricatus L. English Channel. A few valves. 



S. European. 

 Cardium papillosum Poli. Channel Islands. 

 Neaera rostrata Spengl. Shetlands. One valve only. 

 Teredo pedicel lata Quatref. Channel Islands. Very rare. 



In drawing up a complete list of the conchological fauna of 

 any district, one is met by the two difficulties — What constitutes 

 a species? and, What amount of evidence establishes a locality? 

 And perhaps we might add in the third place — What are the 

 limits of the British seas? Into these questions it is not proposed 

 to enter, and accordingly the number of approved British species 

 has been stated at "about" 159. But it is obvious that a list 

 which admits on such evidence as '50 miles N. of Hebrides, one 

 valve,' is one which does not lay down a very severe test of entry, 

 and perhaps on a more rigorous scrutiny the number 159 might 

 be considerably reduced, in which case the number of absentees 

 from the MacAndrew collection, small as it now is, would become 

 considerably smaller. I may mention, however, that while generally 



