of Edinburgh, Session 1881-82. 
703 
of the ventral plates, the ventral paxillae are more widely spaced than 
the dorsal ones, and are disposed in regular lines which run from the 
adambulacral plate to the margin, the lines or columns being marked 
off by straight furrows or wrinkles in the membrane. As the paxillse 
are equidistantly spaced in each of these transverse rows, equally 
regular and uniform longitudinal lines are also traceable along the 
ray. In the arm-angle 9 to 10 paxillse stand in each transverse series, 
the same number being maintained until about the outer fifth of the 
furrow. 
Each adambulacral plate stands on the furrow-margin as the 
terminal plate of one of the transverse series above mentioned ; and 
carries a group of 15-20 spinelets resembling a compressed paxilla, 
only rather more robust than those on the ventral plates. Two of 
the spinelets (sometimes three) larger than the rest, slightly flattened 
and tapering to a point, stand at the margin of the furrow. The 
succeeding spinelets are less robust, and pass in gradation to the 
group of outermost spinelets which are about equal in size to those 
of the ventral p'axillae. The 5 or 6 innermost adambulacral plates 
have much larger spinelets than the others. About 7 5 adambulacral 
plates may be counted along the furrow. 
The united mouth-plates form a sharp angle inwardly, and a large 
elongately ovoid, sub-tubercular swelling is developed on their 
superficies, — the whole surface being covered with spinelets arranged 
in somewhat similar series to the ambulacral spinelets, standing 
perpendicular, 7 to 8 along each side of the mouth angle. The aboral 
portion of each plate is occupied by a compressed paxilliform group, 
similar to those on the adambulacral plates 
Madreporiform body undistinguishable. 
Remarks . — The appearance of this magnificent starfish suggests in 
a remarkable way the association of the prominent external characters 
of a Solaster , a Pentagonaster and an Asterina. It is entirely distinct 
from its northern congeners and in structural formula cannot be 
referred to any genus at present known. Judging from description 
alone it perhaps resembles most nearly the genus Radiaster, recently 
established by M. Perrier* from a specimen obtained by the U.S. Coast 
Survey Steamer “ Blake ” in the dredgings in the Gulf of Mexico and 
the Caribbean Sea. That Mimaster is clearly distinct, however, from 
* Bull. Mus. Covip. Zool., Harvard, vol ix. no. 1, p. 17. 
