1849.] SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 197 



The body of this Biadema is much depressed, so as to give the 

 outline a flattened-out form. The ambuiaeral and interambulacral 

 areas are nearly equal in width, and both bear two ranges of promi- 

 nent, but not very large, primary tubercles, perforated on their sum- 

 mits and with crenulated bases. The areolae of the tubercles are 

 wide, leaving but narrow spaces for the tertiary granules, which are 

 scattered, separate, and rather unequal, and have mostly mammilli- 

 form bases. The granulated space between the two rows of tuber- 

 cles in each interambulacral segment is much wider than that in each 

 ambuiaeral one, where it is reduced to a nearly single undulating line 

 of unequal granules. The mouth is rather large, and has ten con- 

 spicuous notches with reflexed edges around its margin. 



I cannot identify this species with any of those figured by Agassiz 

 and others. It approaches however Diadema superbum, Agassiz 

 (Oxford clay of Switzerland), D. florescens, Agassiz (coral rag of 

 Besan9on), and B. complanatum, Agassiz (Kelloway rock, coral rag, 

 and Oxford clay of France) . 



The specimen described is from the subcretaceous Hmestone of 

 Mamarosa, four leagues south-east of Aveiro. 



Plate XXV. fig. A a. Natural size. 



Fig. 4 b. Magnified. 



Diadema rude, sp. nov. Pl. XXV. fig. 3. 



D. testa depressa, areis ambulacralibus mediocribiis, assulis omnibus tuberculo pri- 

 mario magno ornatis, tuberculis arearum interambulacralium majoribus, tuber- 

 culis secundariis nullis, verrucis minimis inter tubercula sparsis, paucis ; ore 

 lato, margine incise. 



Breadth -f^ inch ; height -^ inch. 



A species quite distinct from the last, though in a very dilapidated 

 condition. The body is depressed with rather rounded sides. The 

 ambuiaeral areas equal in width about two-thirds of the interambu- 

 lacrals. Both are studded with large and conspicuous tubercles on 

 prominent bases, those of the interambulacral plates largest. The 

 spaces between the tubercles have few and scattered granules. The 

 mouth is very wide and its margin notched, but not conspicuously. 



The Biadema placenta of Agassiz, from the coral rag of Soleure, 

 has affinity with this species. Mr. Sharpe's specimen is from the 

 subcretaceous limestone of the Praia de Ma9ams near Cintra. 



Plate XXV. fig. 3 «. Natural size. 



Fig. 3 h. Magnified. 



Toxaster Couloni ? Agassiz. 



A much-injured specimen of an Urchin, too closely alHed to be 

 separated without better materials from the species so named by 

 Agassiz, was found by Mr. Sharpe in the subcretaceous limestone of 

 Figueira. It appears to diifer in having its vertex more central. 

 Toxaster Couloni is a Neocomian species, and all its near allies are 

 either Neocomian or Gault species. 



VOL. VI. PART I. P 



