2 



BRITISH FOSSILS. 



series, parallel to the long axis of the bone. They are smaller in 

 this species than in any other yet discovered, resembling coarse 

 grains of sand ; they, nevertheless, have the radiating lines on the 

 apex, so constant in all the Asteracanthi. The specimen in the 

 British Museum is a fragment of the lower portion of the ray. It 

 measures 7 inches in length. A second fragment, also in the British 

 Museum, measures 5 inches. In these specimens, as is usual in the 

 rays of full grown individuals of the genus, the asteroids are more 

 distant than in the younger ones. They are small in size, and 

 patelliform in figure, the apex being eccentric, and approaching the 

 upper periphery. Their bases are smooth, the stellate rays becoming 

 obsolete before descending so far. The general outline of the ray 

 is very slightly recurved. The anterior margin is rounded, and 

 without carina. The sides expand considerably, so that the back 

 of the fin is broad, as seen in the transverse section (fig. 4). There 

 is no evidence to lead to any conjecture as to the form of tooth 

 belonging to this species ; the only Placoid teeth hitherto discovered 

 in the Tilgate beds being referable to the genera Hyhodus and 

 AcTodus. 



Locality. — The original of figure 1. of the Plate is from the 

 ferruginous grit beds of Tilgate forest, and was presented to me 

 by the late Mr. Dixon. The specimen in the British Museum 

 (figs. 2, 3, 4,) is derived, apparently, from the same beds, and formed 

 part of the Mantellian collection. 



Explanation of Plate. 



Fig. 1. Asteracanthus granulosus, size of nature. 



rig. 2. Asteracantlius granulosus, size of nature. 



Eig. 3. Interior of ditto. 



Fig. 4. Transverse section of ditto. 



Fig. 5. Portion of No. 1 magnified. 



