Asteropsis of Muller and Troschel and Dermasterias of Perrier (1875). Unfortunately, I have not access to Perrier's original paper, but I rely on Sladen's diagnosis of the two genera (“Challenger” Report, p. 355). One differece (I gather both from Sladen and from Bronn's “Thierreichs”) lies in the presence of a distinct “composite reticulated meshwork” formed by the abactinal plates in Dermasterias, while the skeleton of Asteropsis consists of “irregular substellate plates not forming such a network.” From the account of the largest specimens given below it will be seen that in the adult of this species such a “composite reticulated meshwork” does exist, but in other features the genera are quite distinct. The material at my disposal consists of—(a) Large specimens, both dried and in alcohol; (b) Farquhar's type, which is of intermediate size; (c) small ones, dried. (a.) The dried specimens are somewhat compressed and distorted, but the plates are pretty distinctly seen, while in those preserved in alcohol the skeleton is entirely concealed by the tough skin, which is wrinkled on the a bactinal surface, and especially near the tips of the rays, but is smooth on the actinal surface. This skin encloses and connects the adambulacral spines so as to form 2 thick membranes on each side of the groove, one lying in the furrow, the other along its margin. Fig. 1.—Asteropsis imperialis. The central portion of the disc (x 2). ce., central; c.r., centro-radial; i.r., interradial; rl, primary radial. Dimensions.—The dried specimens measure R 75, r 34; R 70, r 31. the alcoholic specimen gives R 56, r 24. Thus r: R=1: 2·20 to 2·33. The form is stellate, with rounded interbrachial angles. The rays are broad at the base (3 mm.), tapering gradually to a rounded apex. At about midway along the ray is 15 mm. across. The figure given by Farquhar represents well the general appearance of a preserved specimen. The madreporite is prominent and round, situated rather nearer to centre than to the margin (as 12 is to 20). The anus is surrounded by a circle of short cylindrical spines, about 10 in number, which close over it. The abactinal skeleton forms an open meshwork, with large papular areas, separated by short rows of narrow flattened ossicles about half as wide as they are long, which radiate from a series of 5- or 6-lobed plates at the nodes of the network. There is a 5-lobed central plate with the anus close ot one side; from it radiate outwards short rods, forming a series of wide meshes around it. At the interradial margin of this circle are 5 irregularly stellate plates, one of which bears the madreporite.