ASTEROIDEA. 21 
ginal plates along the ray; the marginals and adambulacrals do not 
correspond in number or length. 
Four genera: Leptoptychaster, Astropecten, Psilaster, Bathy- 
biaster. 
Subfamily 2, LUIDIIN AL. 
Luidiine, Sladen, Chall. Rep. Ast. (1889) p. xxxi. 
Astropectinide in which the inferomarginal are separated from 
the adambulacral plates by a small intermediate plate throughout 
the ray. Marginals and ambulacrals corresponding in number and 
length. 
One genus: Luidia. 
Family 4. PENTAGONASTERID. 
Pentagonasteride, Perrier, Arch. Mus. vi. (1884) p. 281; Sladen, 
Chall. Rep. Ast. (1889) p. xxxi. 
Phanerozonia in which the marginal plates are very large and the 
diameter of the disk long in proportion to the arms. The skeletal, 
as well as the marginal, plates may be naked or covered with 
granules, are set close, and are rounded, polygonal, or stellate in 
form. 
Two subfamilies. 
Subfamily 1. PENTAGONASTERIN A, 
Pentagonasterinze, Sladen, Chall. Rep. Ast. (1889) p. xxxi. 
Pentagonasteridse in which the abactinal area is covered with 
rounded, polygonal, or paxilliform plates. 
Two (or three) genera: Pentagonaster, Nymphaster, ? Hippas- 
terias. 
Subfamily 2. MIMASTERIN AL. 
Mimasterinze, Sladen, Chall. Rep, Ast. (1889) pp. xxxii & 264, 
“ Abactinal area with small stellate plates bearing true paxille. 
Actinal intermediate areas with imbricating plates in transverse 
series, bearing paxilliform groups of spines.” (Sladen.) 
One genus: Mimaster. 
Family 5. GYMNASTERIID. 
Gymnasteriade, Perrier, Nouv, Arch, Mus. vi. (1884) p. 229. 
Gymnasteriidee, Sladen, Chall. Rep. (1889) p. xxxiii. 
Phanerozonia in which the marginal plates are not all equally 
developed. 
Four genera: Porania, Cheilaster, Rhegaster, and Lasiaster. 
