URASTER. 17 



Amphidetus cordatus, Forbes. Brit. Starf., p. 191. 



— — Agassis and Desor. Ann. des Sc. Nat., 3d series, torn, viii, 



p. 11. 



— Duben and Koren. Kong. Vet. Akad. Hand., 1844, p. 285. 



Body broadly cordate, elevated posteriorly, depressed, and declining anteriorly; sub- 

 angulated at junction of sides and base. All the lateral ambulacra exterior to the ovate 

 coffin-shaped fasciole, the two rows of pairs of pores composing each converging gradually 

 towards their outer terminations. Plates of dorsal surface closely set with minute 

 tubercles, occupying squamated areolae. On the under surface they are larger, and not so 

 closely packed. Anal extremity steep and high : the vent in a slight depression, in its 

 upper part semi-circled by a fasciole, which is incomplete above ; a sub-cordate caudal 

 fasciole below it. Post-oral spinous space broadly lanceolate. Oral ambulacra occupying 

 smooth avenues. Spines fine, curved, slender, fragile, sub-spathulate, well preserved on 

 the specimen described. Length, l-^ths of an inch ; breadth, l T 7 T ths ; height at caudal 

 extremity, 1 inch. 



In the Coralline Crag. 



Order.— ASTERIADtE. 



The true star-fishes have lobed bodies, more or less depressed, and prolonged into 

 radiating arms, more seldom reduced to a pentangular disk. The whole of the upper 

 surface is covered by a coriaceous skin, studded with a reticulation of calcareous plates, and 

 often bearing superficial spines, tubercles, and pedicellariae. There is always a madre- 

 poriform tubercle present ; and generally a vent. In the centre of the ventral surface is 

 the mouth, whence radiate to the extremity of the rays or arms as many ambulacra as 

 there are lobes. In these, the suckers are lodged, ranged in ranks of twos or fours, 

 bordered by peculiar and often spinigerous plates. The only well-defined fragment of a 

 Crag star-fish is a member of the Family Urasteri/E, in which there are always present 

 four rows of suckers in each ambulacral groove. 



Uraster, Agassiz. 



Body deeply lobed, or produced into five (rarely more) slender arms, spinose above. 

 Margins not bordered by conspicuous plates. Suckers four- ranked. 



1. Uraster rtjbens. Plate II, fig. 7, a and b. 



Asterias rubens, Retz. Vetensk. Acad. Hand]., vol. iv, p. 236. 

 — — Linnaiis. S. N., 1099. 



