206 DUBLIN UNIVERSITY 



Saxicava arctica (Linneus). 

 A valve or two was all that occurred of this likely species, which, 

 with its congener Rugosa, was much more abundant in former times than 

 at present, if we may judge from their frequent occurrence in raised sea- 

 beds in so many places. It is still an inhabitant of the bay. 



My a truncata (Linneus). 



Occurred plentifully in the blue clay. One example measured two 

 and three-quarter inches in breadth, and three inches between its 

 lateral extremities. It is still an exceedingly common species in the 

 harbour. 



Mya arenaria (Linneus). 



"Was found everywhere in the silt. One specimen was four inches 

 in length, and two and a half in breadth. It is now a favourite food 

 with the poor along the neighbouring shores, and is known among them 

 by the name Cocklebrillion. 



Corbula nucleus (Lamarck). 

 "Was met with but sparingly in the clay, and generally with sepa- 

 rated valves. It occurs still in the bay. 



Thracia phaseolina (Lamarck). 

 A number of specimens of this species were found, but generally in 

 single valves. It is common enough in the harbour at present, in a 

 fresh state, but dead. 



Thracia pubescens (Pulteney). 

 One rather fine specimen occurred to myself. It has been taken also, 

 but not in the living state, in the bay. 



Thracia convexa ( Wood). 

 A large number of this species, so rare in the living state, was ob- 

 tained in the clay. From the great fragility of the shell, however, not 

 many with both valves could be preserved in the attempt to extricate 

 them from the tough substance in which they were embedded. The 

 specimens were almost all of a fine size. Dr. M'Gee informs me that it 

 occurred to him also abundantly in the excavation for the Prince's Dock. 

 It is noted by Mr. Thompson as having been taken near Belfast, not 

 alive, but with ligament fresh. 



