198 Dr. C. Collingwood on the Nudibranchiate Mollusca 



for about a mile and a half, and rising at intervals into three 

 small islands, called respectively Hilbre, Middle Island, and 

 Little Eye. Hilbre is the largest and most seaward of these ; 

 nevertheless at low water three sides of it are left uncovered by 

 the tide, and it is only a portion of the north-western side which 

 is sufficiently steep and rocky to harbour marine animals. The 

 other two islands are left high and dry at low water. Two miles 

 higher up the river are some rocky prominences named Caldy 

 Blacks, which are seldom visited, partly from their distance, and 

 partly because the tide rushes up the Dawpool Deeps so rapidly 

 and so insidiously, that, without great caution and some expe- 

 rience, the visit is not unattended with danger. Still it is 

 necessary that these rocks should be mentioned, because at least 

 one Nudibranch of rarity and interest has been obtained there. 

 It is the north-west corner of Hilbre Island, however, which is 

 the el Dorado of Liverpool marine zoologists ; and it is really, for 

 its extent, a spot of singular richness, but at the same time 

 sufficiently difficult of access to render a visit to it an event of 

 interest and importance. The low- water mark is fringed with a 

 conspicuous belt of Alcyonium digitatum, interspersed with nu- 

 merous specimens of Sagartia sphyrodeta (Gosse) and Actinoloba 

 diantkus, with here and there an individual of Sagartia viduata ; 

 while immense and beautifully coloured S. crassicornes are clus- 

 tered in masses higher up the rock, together with the ever- 

 varying tints of the little S. troglodytes. Elsewhere the rocks are 

 encrusted with sponges, such as Halichondria panicea and H. ocu- 

 lata ; and in the little rock-pools are abundance of Polyzoa and 

 Zoophytes, such as the delicate Crisia eburnea and the screw-like 

 Bugula avicularia among the former, and Laomedea gelatinosa, 

 Sertularice, Campanularice, and Plumularice &c. among the latter, 

 mingled with the flower-like clusters of Tubularia indivisa. Be- 

 neath nearly every stone may be found numbers of brittle-stars 

 (Ophiocoma rosula and O. tewturata), which harbour there with 

 the two species of Porcelain Crabs, Porcellana platycheles and 

 P. longicornis, particularly the latter, and various species of 

 Terebella, Nereis, and Phyllodoce. In other spots are thickly- 

 planted colonies of the beautiful Fan-Amphitrite {A, ventila- 

 brum), whose variegated and spiral gills often measure as much 

 as 2J inches across. Besides the Crustacea just referred to, 

 there are always to be met with Stenorhynchus phalangium, Hyas 

 araneus, Cancer pagurus, Portunus depurator, abundance of Her- 

 mits (Pagurus Bernhardus and other species) inhabiting shells 

 which vary in size from the largest Buccinum and Fusus to the 

 smallest Mangelia, the iEsop Prawn (Pandalus annulicornis) , 

 and a number of minute Crustaceans, such as Nymphon gracile, 

 Pycnogonum littorale, Lygia, &c, while every weed is alive with 



