REPORT ON THE ASTEROIDEA. 343 
Synopsis of the Genera included in the Family PEnracerorip&. 
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 . A « Pentaceros. 
b. With large spines only. 
a, Supero-marginal plates large. Marginal plates recular 
and correspondent. Form pentagonal. Rays;flat, 
not carinated. Few spines. Large papular areas : . Nidorellia, 
- 8. Marginal plates irregular and not correspondent, 
Form stellate. Many spines. Single pores or 
very small papular areas . . c ‘ . . . 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. : 5 : 2 : 2 . ° 5 . Pentaceropsis. 
Bb. 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 : ° 
: : ; : 9 : . . Culcita. 
b, With papul distributed : not in definite areas. With a pair of 
large marginal plates at the end of the ray . : : A ; . Asterodiscus. 
b. Form stellate. Plates devoid of large granules. 
a. Plates devoid of spines: covered with skin . ; : : , . Choriaster. 
b. Plates bearing large robust spines , 5 5 ; : : « Paulia. 
Genus Pentaceros, Linck. 
Pentaceros, Linck, De Stellis marinis, 1733, p. 21. 
Pentaceros, Schiilze, Betrachtung der versteinerten Seesterne und ihrer Theile, Warschau u, Dresden, 
1760, p. 50. 
Goniaster (pars), Agassiz, Mém. Soc. Sci. Nat. Neuchatel, 1835, t. i. p. 191. 
Pentaceros, Gray, Ann. and Mag. Nat. Hist., 1840, vol. vi. p. 276. 
Oreaster, Miiller 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 Miiller and Troschel’s name of Oreaster, 
proposed in 1842, on the ground that Linck’s name had been applied by Cuvier and 
