2 



BRITISH FOSSILS. 



Fig. 2 a. (upper side) and h. (under side). 



URASTER PRIMiEVUS. 



E. Forbes, in Memoirs of the Geological Survey of Great Britain," 

 vol. ii. part 2, p. 463. 



Diagnosis. U. brachiis quinis^ brevibun, triangularibus, acuminatis ; 

 disco lato. Pagind superiori tuberculatd^ reticulata {spinosd ? spinis obtusis 

 fasciculatis ?) ossiculis ambulacralibus oblongis, latis, geniculatis. 



Description. — Body very broad, pentagonal, produced at the angles 

 into five short lanceolate or elongato-triangular pointed arms, which 

 are each about two-thirds as long as the breadth of the disk. Surface 

 of the disk convex above, as well as the arms tuberculated and reticu- 

 lated, exhibiting traces of having been covered by tufts of short blunt 

 spines. Madreporiform plate sub-central, as well as vent. Beneath 

 nearly flat, the interambulacral spaces reticulated like the upper surface, 

 the ambulacra composed of broad, oblong, geniculated plates, of which 

 there are about twenty in a row. The largest specimens examined had 

 attained the dimensions of an inch and a half in diameter, measuring 

 from arm-tip to arm-tip. 



Affinities, — The general shape of this species reminds us of Asterina, 

 but its structure is so similar to that of the next fossil to be described, 

 that I do not doubt it was a true Uraster. The pointed rays distin- 

 guish it at sight from U. obtusus, its nearest ally. 



Locality and Geological Position. — ^ First found by Mr. John Ruthven, 

 in the Silurian (Ludlow) rocks at Underbarrow, near Kendal. It occurs 

 in a thin sub-calcareous band, loaded with encrinites and trilobites, all 

 rare in the overlying sandstones. Numerous specimens have been col- 

 lected by Professor Sedgwick and Mr. Daniel Sharpe, both of whom 

 have communicated them for examination and delineation. 



Fig. 3. 



URASTER OBTUSUS. 



E. FoRBESj in " Memoirs of the Geological Survey of Great Britain," 

 vol. ii. part 2, p. 463. 



Diagnosis. U. brachiis quinis^ brevibus, convexis, lanceolatis, obtusis ; 

 longitudine brachiarum ad latitudinem disci ut 1 : ossiculis ambu- 

 lacralibus oblongis^ latis^ interstitiis linearibus ; pagind superiori reticidato- 

 spinosd. 



Description. — Body rather broad (being broader than the arms are 

 long), convex above, spinosely reticulate ; the spines were short, and 

 probably grouped in tufts. The arms are short, convex above, broad, 



