132 MYTILID.E. 



water mark to 20 fathoms, on the coasts of Cornwall, 

 Devon, Dorset, and the Channel Isles. The collection 

 of Mr. George Humphreys, the well-known dealer in 

 shells, made in the last century, contained a single 

 valve labelled " Ireland " ; but if the locality was cor- 

 rectly stated, this species has not been rediscovered 

 there. I am only aware of a few (ten) places where it has 

 been discovered in England, though it is tolerably com- 

 mon at Lulworth and Guernsey. Single valves are very 

 abundant in the Coralline Crag at Sutton. M. Martin 

 has found it in the Gulf of Lyons, and Mr. M f Andrew in 

 the Gulf of Tunis and the Canary Isles. 



Dr. Lukis informed me that some of his finest speci- 

 mens were taken alive in a rock-pool lying immediately 

 below half-tide mark on the western shore of Guernsey. 

 They occupied a chink in the rock a little under the 

 surface of the water. The transverse ridges perhaps 

 denote the annual growth of the shell. The fry are so 

 totally dissimilar from the adult, that I was misled into 

 describing and figuring the former under the name of 

 Limopsis pellucida in the ( Annals and Magazine of 

 Natural History ' for January 1859. They are smooth 

 and oval, resembling a minute Ungulina in shape ; the 

 hinge is placed exactly in the middle of the dorsal 

 margin ; and the arrangement of the teeth or crenula- 

 tions on the hinge-line further indicates the affinity of 

 Crenella to Nucula. 



Dr. Leach admirably described this lovely and re- 

 markable shell in his ' Zoological Miscellany ' (1814) as 

 " Modiola Prideaux" Unfortunately the termination 

 of the specific name is not in accordance with the rules 

 of zoological nomenclature, and it must therefore be re- 

 jected. It is true that Capt. Brown altered the name to 

 Prideauxiana in his ' Illustrations of British Concho- 



