18 ECIIIXODERMS OF THE CRAG. 



Abteeias RUBENS, MuUer. Zool. Dan. Prod., p. 2830. 



— — Lamarck. An. sans Vert., 1st ed., vol. ii, p. .512 ; 2d ed., vol, iii, 



p. 160. 



— — Blainville. Man. d'Actin., p. 239, pi. xxii, a, b. 



— GLACIALIS, Pennant. Brit. Zool., vol. iv, p. 60, No. 54. 



— — Fleming. Brit. An., p. AST. 

 Stellonia ecbens, Agassiz. Prod. 



— — Forbes. Wern. Mem., vol. viii, p. 121. 



Urasteh RtJBENS, Forbes. Brit. Starf., p. 83, (with figure.) 

 AsTERACANxniON RUBENS, il/i(//er and Troschel. Syst. der Asteriden, p. I". 



To the commonest of our native star-fishes, I refer a very remarkable and rare 

 fragment from the Red Crag, in the possession of Miss Alexander, who kindly com- 

 uiunicated it for description and representation. 



It consists of a number of ambulacral and other ossicula of an arm of a Uraster, in 

 very perfect preservation. The ambulacral bones are linear, geiiiculated at their inner 

 extremities, and combined to form a ridge. From their outer terminations spring some of 

 the confluent chains of ossicles, that went to the strengthening of the superior arched 

 integument of the arms. 



The specimen is represented in fig. 7, «, of the natural size. Ossicula, probably 

 derived from the same, or a closely allied star-fish, have been found by Mr. Searles Wood. 

 For a description of the Aslerias rubens, the reader may consult the ' History of British 

 Star-fishes.' 



Order.— CRINOIDEA. 



The feather-stars and lily-stars, as the members of this order are popularly styled, 

 differ from all other Echinodermata, in having their reproductive organs attached to the 

 pinnacles of radiating jointed arms. Their viscera are included within a cup of calcareous 

 plates, which, either in the younger stages of growth or throughout life, as appears to liave 

 been the case with most of the fossil species, was borne on the summit of a jointed 

 columnar stem. 



The few remains of Crinoids found in the Crag belong to the Genus Comatula, one of 

 those types of which the adults are free. 



The buccal orifice is in the centre of the visceral disk ; the vent at the extremity of a 

 tube proceeding from it. 



