No. 4. — • The Genus Blakiaster Perrier. 

 By Walter K. Fisher. 



The object of this paper is to present some figures of Blakiaster 

 cOnicus, with notes on one of Perrier's type specimens (No. 247, 

 M. C. Z.) from off Havana, 175 fathoms. I am indebted to the 

 authorities of the Museum of Comparative Zoology for the privilege 

 of examining this specimen. 



There have been only two figures of Blakiaster conicus, the original 

 of Perrier (Nouv. arch. Mus. d'hist. nat., 1884, ser. 2, 6, p. 265, plate 

 9, fig. 2), too small alone to be of service, and a drawing by Verrill 

 (Trans. Conn, acad., 1899, 10, p. 218, pi. 27, fig. 7) of two actinal 

 pedicellariae. The accompanying photographic figures and drawings 

 are published in the hope that they will serve as an aid to identifica- 

 tion, should this genus be found in other parts of the world. 



The specimen is small (R = 26 mm.) and is possibly immature. 

 The abactinal plates are subcircular in general form, with six or seven 

 short lobes, by which they imbricate; the median radials are more 

 definitely hexagonal with short lobes; the proximal plates of the 

 radial series are surrounded by smaller secondary plates, six about 

 each, but not extending far along the ray. The plates bear a low 

 convex tabulum, not so high as the width of the plate, surmounted 

 by a divergent group of short spinelets, the central the stoutest. 

 These spinelets are microscopically thorny. The plates although 

 paxilliform are not typical paxillae. Those on center of disk are 

 slightly smaller, on account of the smaller secondary plates being 

 more numerous. One series of plates reaches the terminal plate 

 which is conspicuous and well shown in the photographic figure 

 (Plate 1). Papulae are single, and are absent from center of disk 

 and a median radial streak. Ordinarily there are about six surround- 

 ing each plate. 



The marginal plates are massive and opposite. The superomar- 

 ginals are covered with delicate spinelets which become shorter and 

 coarser, consequently more granuliform, on the abactinal surface. 

 There are no specialized spines. The inferomarginals are more 

 tumid and bear a lateral, oblique, transverse series of two or three 

 appressed, delicate, needle-like spines, shown on one ray in the photo- 

 graph (Plate 1). They resemble the inferomarginal spines of Per- 



