REPORT ON THE ASTEROIDEA. 



343 



Synopsis of the Genera included in the Family PentacerotiDjE. 



A. Marginal plates conspicuous, defining the ambitus. Abactinal plates in 

 more or less regular longitudinal series, superficially distinct. * 



a. Abactinal plates regular, with more or less definite intermediate 



papular areas. No intercalated series of plates between the 

 supero-marginal and infero-marginal plates. Prominent mammil- 

 lated tubercles or spines may be present. 



a. With large localised mammillated tubercles or spines. Rays 



carinated. Supero-marginal plates small. Form stellate . . . Pentaceros. 



b. With large spines only. 



a. Supero-marginal plates large. Marginal plates regular 

 and correspondent. Form pentagonal. Rays]flat, 

 not carinated. Few spines. Large papular areas . . Nidorellia. 



/3. Marginal plates irregular and not correspondent. 

 Form stellate. Many spines. Single pores or 

 very small papular areas ....... Amphiaster. 



b. Abactinal plates irregular, large and small intermixed, not forming 



definite intermediate papular areas. An intercalated series 

 of plates present between the supero-marginal and infero- 

 marginal plates. No prominent mammillated tubercles or 



spines . Pentaceropsis. 



L'. Marginal plates hidden or inconspicuous and not visibly defining the am- 

 bitus. Abactinal plates not in superficially discernible longitudinal 

 series. 



a. Form pentagonal. Plates usually with more or less numerous large 



tubercular granules. 



a. With large papular areas. No large marginal plates at the end 



of the ray ........ . Culcita. 



b. With papulre distributed : not in definite areas. With a pair of 



large marginal plates at the end of the ray Asterodiscus. 



b. Form stellate. Plates devoid of large granules. 



a. Plates devoid of spines : covered with skin Choriaster. 



b. Plates bearing large robust spines Paulia. 



Genus Pentaceros, Linck. 



Pentaceros, Linck, De Stellis marinis, 1733, p. 21. 



Pentaceros, Schulze, Betrachtung der versteinerten Seesterne und ihrer Theile, Warschau u. Dresden, 



1760, p. 50. 

 Goniaster (pars), Agassiz, Mem Soc. Sci. Nat. Neuchatel, 1835, t. i. p. 191. 

 Pentaceros, Gray, Ann. and Mag. Nat. Hist., 1840, vol. vi. p. 276. 

 Oreaster, Mtiller and Troschel, System der Asteriden, 1842, p. 44. 



I entirely concur with Professor Perrier in the justice of maintaining Linck's name 

 of Pentaceros for this genus, in preference to Muller and Troschel's name of Oreaster, 

 proposed in 1842, on the ground that Linck's name had been applied by Cuvier and 



