Sea Lilies. 3 



is in the Liverpool Museum, and the third iu the museum of 

 Queen's College, Belfast. 



This form has usually been described under the name of 

 Pentaceinus Gaput-Medusce. Another and a widely different 

 species, Pentaceinus Briareus, from the Lias of the south of 

 England, seems, however, to have a just claim to be recognized 

 as the type of the genus Pentacrinus. I think there is great 

 advantage in retaining old and well-known generic terms to 

 indicate marked groups of allied forms; I shall, therefore, 

 merely propose for this species, and one or two fossils which 

 closely resemble it, the rank of a sub-genus, Cenoceinus.* 



Cenocetnus Gaput-Medusce (Mill.) consists of two well- 

 marked divisions, a stem and a head. In the specimen figured 

 the stem seems to rise from a crevice in a stone. There is no 

 doubt that the animal when living is attached to some solid body, 

 but there are good reasons for suspecting that in the present 

 case the attachment is artificial. The stem of this specimen 

 was probably originally much longer ; and, from the analogy of 

 fossil species, it was most likely attached by a wide base. The 

 stem consists of a series of flattened 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, through 

 which one might pass a fine needle in the centre. This hole 

 forms part of a canal, filled during life with gelatinous nutrient 

 matter, which runs through the whole length of the stem, 

 branches in a remarkable 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 

 either surface of the stem-joint there is a very graceful and 

 characteristic figure of five radiating, oval, leaf-like spaces. 

 Each space is surrounded by a border of minute alternate 

 ridges and grooves. The ridges of the upper surface of a joint 

 fit into the grooves of the lower surface of the joint above it; 

 so that though, from being made up of many joints, the stem 

 admits of a certain amount of motion, that motion is very 

 limited. 



As the border of each star-like figure exactly fits the border 

 of the star above and below, the five leaflets within the border 

 are likewise placed directly one above the other. Within 

 these spaces the limy matter which makes up the great bulk 

 of the joints, is more loosely arranged than it is outside, and 

 five oval bands of strong fibres pass right through the joints, 

 from joint to joint, from one end of the stem to the other. 

 These fibrous bands give the column its great strength ; it is 



* Irom two Greek words, Kaivor), recent, and npivov, a lily. 



