2 



BRITISH FOSSILS. 



and can certainly offer no objections to the adoption of the specific appel- 

 lation petalifera^ in preference to the other names cited in onr synonyms. 



Parkinson gave a creditable figure of this curious sea-urchin, along with 

 that of another and very distinct species (the Salenia ornata of Agassiz, 

 MSS.), which has often been cited by mistake as identical with its com- 

 panion. Defrance identified a French species with Parkinson's, and 

 adopted Desmarest's manuscript name of petalifera. It would appear, 

 however, from the statement of Professor Agassiz, in his monograph of 

 Salenice, that Defrance himself used the name per sonata for a fossil which 

 the distinguished naturalist of Neuchatel regards as the type of the 

 species before us. The Salenia figured by Goldfuss, under the name of 

 Cidaris scutiger^ does not seem to me to differ essentially from our Bri- 

 tish species, and I cannot see those distinctions which Agassiz has pointed 

 out between it and the one we figure, at least in Goldfuss's excellent 

 representation ; though that figured by Agassiz himself as scutiger^ cer- 

 tainly presents differences, especially in the indentations of the sutures 

 of the anal plates, which may indicate a distinct variety if not species. 



Description. — Body subglobose, depressed above, divided into five 

 equal portions by the five series of ambulacral plates, which stand out 

 rather more prominently than the interambulacrals. Anal disk broad 

 and slightly convex in some specimens, much more so than in others ; 

 its outline is slightly sinuous. The centre of it is occupied by the supra- 

 anal plate, which is of a hexagonal shape, broader than long, prominent 

 dorsally and centrally, excavated in form of crescent to make the anterior 

 margin of the anus. In front of it is the anterior ovarian plate, lyrately 

 oblong, longer than broad, broadest posteriorly and centrally, perforated 

 in the centre by a large ovarian pore. The lateral ovarian plates are 

 similar in form, but rather shorter. All have their frontal or free 

 margins prominent in the centre. The posterior ovarian plates resemble 

 the others, except that their superior and inner angles are truncated 

 crescentically, and strongly margined, to go towards the formation of the 

 anal rim. They are all perforated by ovarian pores, more or less 

 marginated. In many specimens the anal rim partially encroaches on 

 the posterior ovarian pores. The ocular plates are of much smaller 

 dimensions, transversely and subtriangularly oblong, their inner sides 

 forming the prominent portions of the triangle, and their frontal margins 

 the bases. Their inner sides unite with the inferior and lateral parts of 

 the neighbouring ovarian plates, the superior and lateral parts of which 

 unite with each other, and their superior margins with the supra-anal 

 plate. At the angles of junction of every three plates is a deep exca- 

 vation or punctation, and another in the centre of the line of union 

 between every two plates. Thus there are nine punctations around the 

 borders of the three anterior ovarian plates, six around each of the pos- 



