JOTTINGS FROM MY NOTE-BOOK. 215 



Isocardia COR, Lin. 



[Read 16th August, 1887.] 



This mollusc has been considered a doubtful in- 

 habitant of the Firth of Clyde. In the dr edgings of 

 the yacht Medusa, fragments of Isocardia are often 

 met with. On one occasion two valves, still connected 

 by their ligament, were taken off the Holy Isle, 

 Arran, by Dr. J. R. Henderson, Madras ; but not till 

 the 25th of last month were two taken in one haul, 

 and three in another, in the same yacht, at a depth 

 of from 90 to 98 fathoms between Cumbrae Light- 

 house and Brodick Bay, bottom soft mud. One of 

 the two shells obtained together is an adult, and the 

 other a little smaller ; both are of a dark-brown 

 colour, approaching to black at the sides. The largest 

 of the other three is about an inch in diameter, and 

 the smallest about the size of a pea ; all are of 

 a yellowish-white colour, the largest having an 

 irregular thin dash of reddish-brown along the 

 anterior sides. Jeffreys states the habitat of this 

 species to be " muddy ground in 4 to 40 fathoms," and 

 Forbes " at a depth of 15 fathoms, and dead shells 

 off Skye in 40 fathoms." I have one in my collection 

 taken off the Mull of Galloway in 140 fathoms. 



It is a curious fact that all the valves that were 

 obtained in the Firth of Clyde, with the exception 

 of the two taken together off the Holy Isle, were 

 fragmentary and quite white, with no marks of 

 attrition. How they were so broken in soft mud it 

 is difficult to conjecture. If the catfish (Anarrhicas 

 lupus, Lin.) had been an inhabitant of the Firth of 

 Clyde (as it is not, so far as I know), it might have 

 been suspected of damaging the shells, as its food 

 consists chiefly of mollusca, which its strong teeth 

 are well suited for crushing. In the absence of these 

 fish, however, we must look to some other cause for 

 the broken shells. 



