REPORT ON THE ASTEROIDEA. 489 
bulacral plates composed of transverse combs of spines united by web-tissue. It differs 
from both genera in its transparent supradorsal membrane devoid of muscular fibrous 
bands, by the possession of three pairs of free secondary or superficial mouth-spines, and 
by its true pentagonal form. 
Chorology of the Genus Calyptraster. 
g 
Geographical distribution :— 
ATLANTIC: One species between the parallels of 0° and 15° 8, 
Calyptraster coa, off the coast of Brazil, south-east of Per- 
nambuco. 
ee) 
. Bathymetrical range: Uncertain ; between 32 and 400 fathoms. 
y. Nature of the Sea-bottom: Red mud. 
Chorological Synopsis of the Species. 
Ocean. Range in Fathoms. | Nature of the Sea-bottom. 
Calyptraster coa . : ; Atlantic. 32 to 400 | Red mud. 
1. Calyptraster coa, Sladen (Pl. LXXVIII. figs. 1 and 2; Pl. LX XIX. figs. 1-3). 
Calyptraster coa, Sladen, 1882, Journ. Linn. Soe. Lond. (Zool.), vol. xvi. p. 207. 
Marginal contour pentagonal, interbrachial arcs very slightly incurved. Minor radial 
proportion 68 per cent. R=11mm.; 7=7°5 mm. Abactinal surface flat, or even some- 
what concave in consequence of the rays being slightly curved upward ; radial areas not 
specialised externally, the supradorsal membrane forming a plane area. No marginal 
fringe. Actinal surface convex. 
The supradorsal membrane is extremely thin and perfectly hyaline, a clean specimen 
appearing to the eye as transparent as glass. No muscular bands are present, although a 
fibrillar strueture may be seen in the tissue under high magnification. The spiracula are 
rather large, numerous, and uniformly distributed. The paxille have long pedicles, and 
are moderately delicate, evenly and equidistantly placed; the crown is usually composed 
of five spinelets, which are short in comparison with the pedicle, and rather delicate. A 
few of the spinelets taper a little at their extremity, but usually they are slightly flaring. 
(ZOOL. CHALL, EXP.—PART LI.—1888.) 62 
