REPORT ON THE ASTEROIDEA. 133 
Synopsis of the Species included in the Genus Porcellanaster herein described. 
A. One cribriform organ in each interbrachial are. Adambulacral plates with two 
or three spines. No segmental pits or papille. 
a. Rays short. Abactinal membrane with spinelets confined to limited areas . cxeruleus. 
b. Rays long. Abactinal membrane entirely covered with spinelets. 
a, Rays tapering. Spines on each supero-marginal plate, long and 
delicate. Terminal plate small, with five spines. Spinelets 
of disk clavate ; : ¢ : : : ; : : caulifer. 
6. Rays broad and robust. Spines on two plates only, stout. Terminal 
plate large and tubercular, with three spines. Spinelets of 
disk cylindrical : ; : ; : 2 6 : tuberosus, 
B. Three cribriform organs in each interbrachial arc, Adambulacral plates with one 
spine. Segmental pits and papille present. 
a, Rays long androbust. Abactinal membrane entirely covered with spinelets. 
Spines on each supero-marginal plate, long and thick : 3 Crassus. 
b. Rays short and delicate. Abactinal membrane with spinelets confined Se 
limited areas. No spines on the supero-marginal plates or only rudi- 
mentary : ; ; : : : : : a 5 : gracilis, 
Porcellanaster eremucus is not included in the foregoing table on account of its very 
immature condition. To place the characters presented by such an early phase of growth 
in comparison with those pertaining to the adult stage of the forms above mentioned 
would clearly be not only useless but misleading. 
Two species of Porcellanaster are “named” by M. Perrier’ amongst the material 
dredged by the ‘‘'Talisman,” but no description has been published. ‘The forms conse- 
quently cannot be recognised. 
Chorology of the Genus Porcellanaster. 
a, Geographical distribution :— 
ATLANTIC: Two species between the parallels of 50° N. and 40° S. 
Porcellanaster cxruleus off the eastern coast of the United States 
of America. Porcellanaster eremicus midway between the Cape of 
Good Hope and the Island of Tristan da Cunha, 
Paciric: Three species between the parallels of 40° N. and 40° S. 
Porcellanaster tuberosus off the coast of Japan, south of Kawatsu. 
Porcellanaster crassus in the mid south Pacific, near the meridian 
of 135° W., approximately midway between Sydney and Valparaiso. 
Porcellanaster gracilis off the western coast of South America, 
between Valparaiso and the Island of Juan Fernandez. 
1 Comptes rendus, 1885, t. ci. p. 886. 
