68 Becoi'ds of the Results of Dredging. 



Art. II. Records of the Residts of Dredging. 

 By Edward Forbes, Esq. 



Having been of late in the habit of dredging on a part of 

 the coast which has not been examined, it has occurred to me 

 that the communication of some of the results of my labours 

 would not be without its use, availing myself of the oppor- 

 tunity of making some remarks on the genera and species 

 allied to the subjects of my notice. 



The scene of my limited researches has hitherto chiefly lain 

 in the Irish Sea, on the coasts of the Isle of Man ; and, the 

 ground being new, I have found my exertions amply rewarded 

 by the addition of many of the scarcer British Testacea to 

 my collection. On the northern coast of that island, at the 

 distance of from three to seven miles from land, there is a 

 scallop bank many miles long, in twenty fathoms water, which 

 is especially prolific in conchological treasures. Venus cas- 

 sina and fasciata, Cardium laevigatum and fasciatum, Pecten 

 maximus, varius, and obsoletus, abound upon it. Its prin- 

 cipal inhabitants are the Pecten opercularis and the oyster ; 

 which j however, is large, coarse, and ill-flavoured. Adhering 

 to oysters, there are Emarginula fissura, Fissurella grse N ca, 

 Capulus hungaricus, Chiton cinereus, and more rarely Chiton 

 lae\is and fascicularis. Velutina laevigata is also not uncom- 

 mon. In the cavities of dead shells of Venus virginea, KehVa 

 suborbicularis occurs; and sometimes Trochus striatus. 

 Trochus tumidus is very abundant. Pectunculus pilosus and 

 Cytherea exoleta are very frequent. Mactra elliptica also 

 occurs ; but Mactra solida and truncata, which abound on 

 most of the Scottish shell banks, have not been found as yet 

 on the Manx coast. On the edge of the bank, where gravel 

 predominates over mud, univalves are more frequent than 

 bivalves ; and J5uccinum undatum and striatum, Fusus anti- 

 quus and corneus, fill the dredge. The Fusus antiquus 

 attains a very large size on the southern coasts of the island, 

 but on the north side it is generally dwarfish. The little 

 Fusus muricatus is also frequent; and Trochus zizyphinus 

 and papillosus are not rare. The white variety of T. zizy- 

 phinus occurs at times ; the animal differs in no respect from 

 that of the T. zizyphinus. Trochus magus is found, but always 

 dead and worn ; and the mouth is frequently filled up with a 

 most beautiful and singular animal of the Actinia kind, to 

 which I shall refer hereafter. 



Starfish of the Ophiura kind abound on the edge of the 

 shell bank; they are often so plentiful as to fill the dredge. 

 Two species occur, the O. rosula and O. lacertdsa. When 



