REPORT ON THE ASTEROIDEA. 61 
and the contingent horizontal margins of both plates are consequently straight. The 
plates of both series usually armed with one more or less prominent thorn-like spine, but 
this may be aborted or may be absent, especially in young forms. The general surface 
of the plates of both series covered with short papilliform spinelets or granules. 
Abactinal area with small rounded scale-lke plates, bearing small pseudo-paxille, more 
or less well-developed, and usually forming a closely packed covering. No definite order 
of arrangement. Papule numerous and generally distributed. 
Actinal interradial areas well-developed, with numerous intermediate (ventral) plates, 
arranged in more or less definite columns, but often difficult to distinguish. 
Armature of adambulacral plates consisting of :—(1.) A longitudinal furrow series of 
short spines, usually compressed laterally, subprismatic and lamelliform, standing parallel 
to one another. (2.) One or more longitudinal series of papilliform spinelets or granules 
on the actinal surface; in some forms the first series are well-developed spinelets, and 
nearly as large as those of the furrow series ; and in some there is a single enlarged spinelet 
amongst the first series. 
Madreporiform body very large, compound, placed near the marginal plates, covered 
with paxillee. 
Pedicellarize (subvalvuliform) may be present on the abactinal and actinal interradial 
areas. 
Anal aperture subcentral. 
Actinostome widely expanded, with large fleshy lip. 
Synopsis of the Species included in the Genus Dytaster herein described. 
A. With a single long secondary spine on the actinal surface of the adambulacral re 
Lateral margins of the rays angularly rounded . : , spinosus. 
B. No long secondary spine on the actinal surface of the adambulacral pte or oe 
represented at the extreme tip. Lateral margins of the rays vertical. 
a, With more than one row of secondary spinelets or granules on the actinal 
surface of the adambulacral plates 5 ; ; : . 
a. With a well-developed series of secondary spines. Ten to twelve 
spinelets in the furrow series. 6 exilis. 
b. Secondary series of spines little more than papalirorm 2 pendiee ii 
five or six true spinelets in the furrow series. 
a, Supero-marginal and infero-marginal plates with prominent 
spines. 
i, Disk small, rays long. With pedicellarie on the actinal 
surface. r : : , . madreporifer. 
. Disk large, rays eaunaaegehcir led No pedicellariz on 
the actinal surface. . nobilis. 
8. Supero-marginal plates with a paberele infer: aieinall lates 
with an aborted spine 5 . : xquivocus. 
b, With only one row of secondary granules on the adambalacral Petes 
a, Marginal plates armed. Actinal interradial areas well developed ‘ biserialis. 
b, Marginal plates unarmed. Actinal interradial areas very small . : inermis. 
