WEST INDIAN STAEFISHES 



123 



Genus Cheiraster Studer. 



Cheiraster Studer, Sitzungs. Naturf. Freunde, Berlin, xvi, pp. 130, 131, 1883; 

 Anhang z. d. Abhandl. d. k. preuss. Akad. Wiss. Berlin, pp. 49, 51, 

 1884. (Type is C. gazellce Studer.) Perrier, Exped. Trav. et Talis- 

 man, p. 269, 1894. Sladen, op. eit., 1889, pp. 3, 25. Ludwig, Notom- 

 yota, pp. 442, 454, 1910. Fisher, op. cit., 1911&, pp. 120, 123. 



Pontaster (pars) Sladen, op. cit., pp. 23, 25, 1889. (Type of Pontaster is 

 P. tenuispinus.) 



Benthopectinidae which normally have no odd interradial mar- 

 ginal plates. The papulae, situated at the base of the rays, are 

 not gathered into a special, median papularium, but form a bi- 

 lobed group, often U-shaped or V-shaped, which, in the adult, 

 may contain many papulse and cover most of the base of the ray 

 and extend on the disk but in the young it may contain only one 

 to three or four pores and show no evidently bilobed character. 

 The apex of the group is directed toward the disk. 



The central part of the disk may, in the adult, bear a cluster 

 of more or less numerous long acute spines, but these are few or 

 lacking in the young, and in the adults of some species. 



The dorsal surface is closely covered with low, round or angu- 

 lar irregularly arranged parapaxillae or spinoparapaxillae. A 

 boss or short columnar process arises from the flatish plates, and 

 is surmounted by a stellate marginal series of spinules or gran- 

 ules, and with one or several central spinules, which may be 

 spiniform in some species, or granule-like in others. Distally 

 the radial plates may become flatter, minute protopaxillae. 



The two rows of marginal plates are well-developed and usual- 

 ly decidedly alternate, and more or less angular, with oblique 

 sutures. Each plate of both series usually bears one large acute 

 marginal spine ; often one, especially the lower one, may have one 

 or several smaller secondary spines around its base. The surface 

 of these plates is covered with small spinules or spiniform gran- 

 ules, larger beneath; the inferomarginals may also have one or 

 two transverse rows of spines beneath, in some species. 



The proximaUy angular adambulacral plates have a marginal 

 series of numerous slender graded spines on the inner edges, 

 which is continuous with a series of smaller spines around the 

 outer margin. In the center of its actinal surface, each plate 

 has one or two, or sometimes alternately one and two, larger, 

 acute, usually erect spines. 



