1849.] SHARPS ON THE SECONDARY ROCKS OF PORTUGAL. 195 



Found in Jurassic limestone at Montemor-velho. 



Only one fragment of this shell has been found, which is not suf- 

 ficient to furnish a good specific description ; yet it is of too much 

 interest to be omitted, both from the rarity of Turrilites in beds of 

 this age, and from this species presenting a character of ribbing not 

 before seen in the genus : its flattened spire connects it with the 

 Ammonitiform species of Turrilites, T. Valdani, T. Coijnarti and 

 T. Boblayei, described by M. D'Orbigny, all of which, like this shell, 

 are of the age of the has. 



Description of Fossil EcHiNiDJE/rom Portugal. 

 By Professor E. Forbes. 



Echinus Olisiponensis, sp. nov. Pl. XXV. fig. 1. 



E. assulis numerosis, angustissimis, dense tuberculatis ; tuberculis primariis parvis, 

 sequalibus, in seriebus horizontalibus nndulatis dispositis ; poris ambulacralibus 

 omnibus in seriebus triplicibus obliquis dispositis. 



This pretty species belongs to the group of Echini which Agassiz 

 has separated as a genus under the name of Polycyphiis, distinguish- 

 ing the section from his (not Gray's) Arbacia, with which it has a 

 common habit and the character of a general diffusion of numerous 

 equal tubercles over the plates, by the pores being arranged in triple 

 series instead of in a single line. But the latter character I have 

 shown elsewhere (British Organic Remains, Dec. 1. pl. 6) to be 

 fallacious, and a misinterpretation of the true structure, which in no 

 essential respect diifers from that presented by the genus Echinus ; 

 nor can Polycyphus be regarded in any other Ught than as a sub- 

 division of the same genus of no great value. 



The species before us is regularly melon-shaped, but without any 

 rugosities or inequalities of its sides. The whole surface, divided into 

 five broad and five narrow segments by two ambulacra, is studded 

 with small, equal, but conspicuous tubercles ; the interstices between 

 them are covered with miliary granules. The interambulacral plates 

 towards the centre (regarding their horizontal dimension as the length) 

 are very long and narrow ; those towards the middle bear about 

 six tubercles, arranged in a somewhat undulated fashion, each row, 

 ascending towards the ambulacra and again towards the interambula- 

 cral suture, depressed in its centre. The total number of tubercles 

 arranged across the centre of an interambulacral area is consequently 

 twelve. The ambulacral plates bear similar tubercles, two on each 

 plate. Opposite each interambulacral plate, there are in each ambu- 

 lacrum three pairs of pores, each series of three pairs arranged ob- 

 liquely and with a slight undulation of direction, but not overlapping 

 the commencement or termination of the next series. This arrange- 

 ment is constant and similar from the mouth to the vertex. The 

 mouth is circular, and distinctly notched near each ambulacrum. The 

 anal and ocular plates have been destroyed in the specimen examined. 



Dimensions. — Breadth \^ inch ; height ^ inch ; breadth of 

 mouth ^ inch ; breadth of anal disk -^^ inch. Number of interam- 

 bulacral plates in each vertical series about 22. 



