96 FOSSIL ASTEROIDEA. 



magnitude, but also by the manner in which the upper surface is turned over so as 

 to make the ossicle P-shaped (compare Text-fig. 23, p. 119). 



Associated with these marginalia are found rounded, smooth ossicles, which are 

 correspondingly large, being as much as 12 mm. in diameter, and which are 

 undoubtedly ossicles from the abactinal surface of the disc. Their size and form 

 (see PI. XXIX, fig. 6) render them liable to be mistaken for ossicles of Staurander- 

 aster (see p. 125). They do not, however, possess spine-pits, and species of Staur- 

 anderaster which do not possess spine-pits are very distinct, having nodular abactinal 

 ossicles of a very characteristic appearance (compare 8. coronatvs, PI. XXIV, fig. 2). 

 There appears therefore to be no doubt that these ossicles should be referred to 

 the genus Pijcinaster, and probably to P. punctatus. The base of the abactinal 

 ossicles of P. angustatus is produced, as also in P. crassus (PI. XXIX, fig. 4 a), and 

 quite different from the flattened base of these ossicles. 



Remarks. — It might be urged that the differences which separate these ossicles 

 from those ascribed to P. angustatus, are not sufficient warrant for a new species. 

 I regard the differences, however, given above as important, and though several 

 well-preserved specimens of P. angustatus are known, none approaches the large 

 size which P. punctatus must have attained. On p. 81, Pentaceros senonensis, 

 Valette, was regarded as probably identical with P. Boi/sii. Examination of the 

 original specimens, which I owe to the courtesy of Dom Aurelien, shows that they 

 belong to four different species : Stauranderaster coronalus, 8. argus, Pycinaster 

 angustatus, and my " Pentaceros punctatus." The last species is represented by 

 two dorsal ossicles from Les Clerimois (figs. 1 and 2). With the concurrence of 

 Dom Aurelien, I therefore take the original of his fig. 1 as type. 



Locality ami Stratigraphical Position. — The specimens in the possession of 

 Dr. Blackmore are from East Harnham, Wilts., zone of Actinocamax quad rat us. 



3. Pycinaster crassus, n. sp. PI. XXIX, figs. 1, 2, 2 a, 3, 3 a, 4, 4 a, 5. 



Specific Characters. — Body of large size. Height of marginalia not twice their 

 thickness. Median marginalia smooth. More distal margmalia with prominent 

 mammilations. 



Material. — There are about eight fragmentary specimens of this species in the 

 British Museum (Nat. Hist.). The specimen registered E. 2576 (Mantell Coll.) 

 shows considerable portions of the actinal surface, and that registered 35498 

 (Taylor Coll.) the dorsal view of a well-preserved portion of one arm. Both these 

 are figured on PI. XXIX. Another specimen, registered E. 2628 (Mantell Coll.), 

 shows a portion of the abactinal surface of the disc. The other specimens are 



