ANNALS OF NATURAL HISTORY. 



XXIII. — On a Shell-bank in the Irish Sea, considered Zoolo- 

 gically and Geologically, By Edward Forbes, Esq. 



A H OR the last seven years I have been in the habit of dred- 

 ging on a scallop bank which lies about five miles off the coast 

 of Ballaugh on the north-western side of the Isle of Man. My 

 observations have generally been made in autumn, and have 

 been regularly recorded as soon as the contents of the dredge 

 had undergone examination. The number of species and the 

 number of specimens, dead and living, were duly noted down ; 

 always of the mollusca, and generally of the zoophytes and 

 radiata. The want of a sufficient acquaintance with the 

 Crustacea and ann elides has prevented my keeping any me- 

 morial of the numbers caught : the specimens were however 

 generally preserved. From this bank I have obtained many 

 new and rare animals, descriptions of some of which have been 

 published. The observing of such, however, was not the only 

 object in view, but also the observing the manner in which 

 the various species there living are associated together, and 

 the changes which their habitat undergoes from time to time, — 

 points in zoology especially useful to the geologist. The re- 

 sults, so far, of my researches in this interesting locality, I 

 propose in this paper briefly to communicate. 



The bank, properly so called, is about twenty fathoms be- 

 low the surface of the sea, and is thickly covered with scal- 

 lops {Pecten opercalaris), among which the common Oyster, 

 the Pecten maximus and P. varius, and many other shells are 

 found in smaller numbers. The ground at the edge of the 

 bank is gravelly, with few scallops, but many univalve shells, 

 such as Murex erinaceus, Trochus zizyphinus, and Natica Al- 

 deri. Between the bank and the shore, but nearer the latter, 

 is a great tract of fifteen fathoms and under in depth, where 

 great quantities of Laminaria and other marine plants grow, 

 and which is covered with stones of considerable size, similar 



Ann, Nat. Hist. Vol.4. No. 24. Dec. 1839. r 



