REPORT ON TILE ASTEROIDEA. CI 



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-like plates, bearing small pseudo-paxillse, more 

 or less well-developed, and usually forming a closely packed covering. No definite order 

 of arrangement. Papulae 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 paxillae. 



Pedicellarice (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 plates. 



Lateral margins of the rays angularly rounded ...... spinosus. 



B. No long secondary spine on the actinal surface of the adambulacral plates or only 



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 ...... 



a. With a well-developed series of secondary spines. Ten to twelve 



spinelets in the furrow series ...... exilis. 



b. Secondary series of spines little more than papilliform granules. Only 



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 pedicellaria? on tbe actinal 



surface ......... madreporifer. 



ii. Disk large, rays comparatively short. No pedicellariae on 



the actinal surface ....... ndbilis. 



/3. Supero-marginal plates with a tubercle, infero-marginal plates 



with an aborted spine ...... sequivocus. 



b. With only one row of secondary granules on the adambulacral plates. 



a. Marginal plates armed. Actinal interradial areas well developed . biserii 



b, Marginal plates unarmed. Actinal interradial areas very small . . itu r 



