REPORT ON THE ASTEROIDEA. 233 



extremity, form a broad and conspicuous margin to the disk and rays. Each plate is 

 slightly tumid ; and midway along the ray their breadth is greater than that of the paxillar 

 area, the latter contracting outwardly into a mere narrow strip. The length of the 

 plates is about two-thirds of their breadth, and their height is about one-half the breadth. 

 The abactinal and lateral areas of the plate are united by a well-rounded curve : the 

 tumidity above mentioned being conspicuous there. The surface of the plates is covered 

 with low, robust, granuliform papillae, which become small and crowded in the regions of 

 the transverse margins, there being a great disparity in size between these and the robust 

 granule-like papillae along the median line of the plate. This disparity, however, may 

 vary in degree ; and sometimes one or more of the papillae on the tumidity or rounding 

 are larger than the rest, and even simulate a small supero-marginal tubercle or low conical 

 spinelet. The majority of the supero-marginal plates bear one or even two pedicellarise 

 of simple formation, but each in relation with a pit in the plate, and frequently simulating 

 very suggestively some of the foraminal or " excavate " forms of the organ found in the 

 Pentagonasteridae and allied families. 



The infero-marginal plates correspond exactly to the superior series, and their breadth 

 on the actinal area is as great as that of the superior series on the abactinal area. 

 Their surface is covered with papillae, which become large, flattened, and squamiform in 

 the median region of the plate towards the end adjacent to the adambulacral plates. Each 

 plate bears at the upper end on the aboral margin a slightly oblique row of three small, 

 delicate, cylindrical, taperiDg spinelets, standing close together, subequal, rather longer 

 than the plate, and appressed to the side of the ray. On the inner half of the ray there is 

 frequently one or even two similar spinelets on the aboral margin of the plate between this 

 series and the end of the plate adjacent to the adambulacral plates, but always widely 

 separate. Sometimes four spinelets are present in the oblique lateral series, the upper- 

 most beinc; rather smaller than the others. 



The adambulacral plates are large and massive, rather longer than broad, and with a 

 sli^htlv convex margin towards the furrow. Their armature consists of a furrow series of 

 ten long, thin, very delicate, cylindrical spinelets, subequal in length, which is about 

 equal to that of the plate, and standing subparallel. In a large example these spinelets 

 are slightly compressed laterally, and all are covered with a very thin membrane. On the 

 actinal surface of the plate are about three irregular longitudinal rows of spinelets, with 

 five or six in each, which are short, tapering, pointed, and covered with membrane, the 

 whole forming a group rather than regular series. The length of the spinelets on the 

 actinal surface of the plate is much shorter than that of the furrow series, and diminishes 

 as the spinelets recede from the furrow. 



The mouth-plates are elongate and narrow, and the united pair are subelliptical and 

 prominent actinally. Their armature consists of a marginal series of very small, short, 

 tapering, and rather widely spaced spinelets, which are closely appressed to the superficial 



(ZOOL. CHALL. ESP. PART LI. 1888.) 30 



