REPORT ON THE ASTEROIDEA.” 535 
Family EcHINASTERID&, Verrill, 1871 (1867), emend. 
The family Echinasteridw established by Verrill’ comprised the genera Echinaster, 
Acanthaster, Mithrodia, and Ferdina. In 1875 Perrier? added to this group Solaster 
(including Crossaster), Cribrella, and Valvaster, and removed the genus Ferdina to the 
family Linckiide. In 1878 Viguier* maintained the family as thus constituted, but 
divided the genera into four “tribus,” the Echinasterine, Mithodiine, Valvasterine, and 
Solasterinz, the last embracing the genera Solaster and Acanthaster. In 1884 Perrier‘ 
removed Solaster (recognising the independent genera Solaster, Crossaster, and Lophaster), 
which he placed in a distinct family Solasteride, and Mithrodia, which he also ranked in 
a separate family. With the latter step I am unable to agree, and I have therefore 
replaced the Mithrodiine as a subfamily of Hchinasteride. With this exception I 
maintain the generic constitution of the family as last amended by Perrier. 
I have added two new genera to the family—Perknaster, a form allied to Cribreila, 
and Plectaster, a genus established for the reception of the remarkable species described 
by Miiller and Troschel® under the name of Echinaster decanus, which has since been 
erroneously referred by Perrier® to the genus Solaster. I have recently had the gratifica- 
tion of identifying the species in some examples sent to the British Museum from Port 
Jackson and Port Phillip, respecting which Prof. Jeffrey Bell’ has subsequently published 
a brief note recording the new occurrence of this interesting type. Plectaster, n. gen., is 
characterised by the wide-meshed reticulate arrangement of the abactinal plates, which 
leave enormous papular areas occupied by numerous papule (fifty or more may be counted 
in a large mesh, and the surrounding margin of the membrane perforated by the papula 
is often papillate) ; by the abactinal plates bearing compact groups of short, equal, upright 
spinelets imbedded in a membranous mass; by the presence of actinal intermediate and 
infero-marginal plates (the latter slightly larger) similarly armed with short, equal, 
upright spinelets invested in a sacculate membranous bag, which in spirit specimens 
has the appearance of being deeply invaginated or perforated in the centre; by the 
armature of the adambulacral plates, consisting of two parallel semicircular series of 
short, equal, cylindrical spinelets, four or five in each series, standing upright and 
palisade-like. Plectaster decanus has a remarkable facies unlike that of any other form 
with which I am acquainted. 
1 Trans. Conn. Acad. Arts and Sci., 1871 (1867), vol. i. part 2, p. 343. 
? Révis, Stell. Mus., p. 35 (Archives de Zool. expér., 1875, t. iv. p. 299). 
3 Archives de Zool. expér., 1878, t. vii. p. 93. 
* Nouv. Archives Mus. Hist. Nat., 2e Série, 1884, t. vi. p. 164. 
5 Archiv f. Naturgesch., 1843, Jahrg. ix. Bd. i. p. 114. 
8 Nouv. Archives Mus, Hist. Nat., 2c Série, 1884, t. vi. p. 78. 
7 Zoologischer Anzeiger, March 1888, Jahrg. xi. p. 121. 
