DEEP SEA FAUNA 1315 



These two species belong to the genus Pentacrinus, 

 which is well represented in the beds of the lias and 

 oolite, and sparingly in the white chalk; and are 

 named respectively Pentacrinus asteria, L., and P. 

 mulleri, Oersted. The first of these has been known 

 in Europe since the year 1755, when a specimen was 

 brought to Paris from the island of Martinique, and 

 described by Guettard in the Memoirs of the Royal 

 Academy of Sciences. For the next hundred years 

 an example turned up now and then from the 

 Antilles. 



Pentacrinus asteria may be taken as the type of 

 its order; I will therefore describe it briefly. The 

 animal consists of two well-marked portions, a stem 

 and a head. The stem, which is often from 40 to 

 60 centimetres in length, consists of a series of 

 flattened calcareous joints; it may be snapped over 

 at the point of junction between any two of these 

 joints, and by slipping the point of a penknife into 

 the next suture a single joint may be removed entire. 

 The joint has a hole in the centre, through which 

 one might pass a fine needle. This hole forms part 

 of a canal filled during life with a gelatinous nutri- 

 ent matter which runs through trie whole length 

 of the stem, branches in a complicated way through 

 the plates of the cup, and finally passes through 

 the axis of each of the joints of the arms, and of 

 the ultimate pinnules which fringe them. On the 

 upper and lower surfaces of the stem-joint there 

 is a very graceful and characteristic figure of five 

 radiating oval leaf-like spaces, each space surrounded 

 by a border of minute alternate ridges and grooves. 



