REPORT ON THE ASTEROIDEA, 221 
placed spinelets. A double line is present on the surface of the plate, those near the middle 
line of the mouth-angle being large, robust, compressed transversely, and with tips obtusely 
rounded, and increasing in size towards the inner extremity of the plate. The innermost 
spines of the mouth-angle form a short horizontal comb of four parallel spines directed 
towards the centre of the mouth. The margins of the mouth-plates are fringed with a 
line of about eight small ciliary spines, which decrease in size and robustness as they recede 
from the mouth. 
The madreporiform body, which is small, slightly convex, and with fine striations, is 
placed at about its own breadth distant from the marginal plates. 
The ambulacral tube-feet are pointed, and the extreme tip appears to be very slightly 
thickened. 
The terminal (ocular) plate is elongate, and armed at the extremity with four or five 
short, robust spinelets directed outward. 
Colour in alcohol, brownish grey. 
Locality.—Off Inaccessible Island, Tristan da Cunha. Depth 90 fathoms. 
Remarks.—This species is in many respects a very abnormal Astropecten. So far as 
general formula is concerned its nearest ally in that genus is Astropecten pentacanthus, 
Delle Chiaje, sp., but the facies of the two forms is altogether different, and they could not 
possibly be mistaken. The character of the abactinal paxille (the pedicle being represented 
only by a broad tubercular eminence of the plate) and the great development of the actinal 
interradial areas are altogether unlike any Astropecten with which I am acquainted. It is 
not without hesitation that I have admitted the form into the genus. 
Two specimens of Astropecten obtained by the “Gazelle” near the eastern coast of South 
America (off Buenos Ayres) in lat. 34° 43’ 7” S., long. 52° 36’ 1” W., at a depth of 44 
fathoms, have been referred by Professor Th. Studer? to this species, 
Genus Psilaster, Sladen. 
Psilaster, Sladen in Narr. Chall. Exp., 1885, vol. i p. 611. 
Disk small, Rays moderately long, robust and high at the base, tapering to a pointed 
extremity. 
Marginal plates plane or slightly tumid, not forming a ridge or highly developed 
fasciolar groove. ‘The surface of the plates is covered with small papilliform squamules 
or granules. The supero-marginal plates are devoid of large spines or tubercles. The 
infero-marginal plates may bear several small spinelets, appressed to the ray, disposed in 
series near the lateral margin and usually near the aboral edge of the plate. 
Abactinal’ area with compact paxillz, composed of short papilliform spinelets, and 
arranged usually in regular transverse lines at the sides of the ray. 
1 Anhang z. d. Abhandl. d. k. preuss, Akad. d. Wiss. Berlin, vom Jahre 1884, p. 46, 
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