Prof. W. Thomson on the Depths of the Sea. 113 



Fi-. 1. 



highest interest both from their biological and their geological 

 relations ; and many were new to science. 



One animal form, of which about seventy specimens were 

 foimd, Avas of surpassing interest. It was a " Crinoid " — a 

 stalked starfish, with a delicate thread-like stem three or four 

 inches long, and a head 

 at first sight very closely 

 resembling that of the 

 pentacrinoid larval stage 

 of a feather-star which is 

 common in deep water off 

 the Norwegian coast. A 

 careful examination, how- 

 ever, showed that the 

 crinoid was mature, and 

 that it belonged to a to- 

 tally distinct family of the 

 order, hitherto only known 

 fossil, and supposed to be 

 almost entirely confined to 

 the Mesozoic series of 

 beds. This family is called 

 the Apiocrinidse, from the 

 characteristic genus Apio- 

 rrimiSj of which the spe- 

 cies best known in this 

 country is the " pear- 

 encrinite," which was got 

 in great abundance in a 

 bed of Great Oolite ex- 

 posed in cutting the tun- 

 nel through Box Hill. 

 The group seems to have 

 attained its maximum 

 during the period of the 

 deposition of the oolitic 

 beds in the European 

 area. It is not repre- 

 sented in the earlier for- 

 mations ; but we find 

 handsome well-developed 

 species belonging to several genera in the Jurassic beds on 

 the Continent. In the loAver beds of the chalk there are two 

 or three somewhat obscure forms ; while in the white chalk 

 the family, so far as we know, is represented by a single species 

 of a single genus, Bourgueticrmus elh'pticus, in which the head 



n 



Rhizocrinus lofotensis (Sara). 

 (Four times the natural size.) 



