60 NATURAL HISTORY BULLETIN 



llmm . ratio, 1 :1.8. It is the same one from which figures of the 

 details of structure have been made. 



The rays are convex ; ends obtuse. All the plates of the upper 

 side were naked, as received, dried. Probably they had some 

 spinules originally. The plates are minutely punctulate, and 

 closely imbricated. 



Two alternating rows of plates, slightly larger than those ad- 

 jacent, take the place of a median radial row. They are angu- 

 larly shield-shaped. The adcentral edge is slightly raised and 

 emarginate to accommodate the single papula standing there. 

 No small intermediate plates are now left. 



The plates in the rows of the sides of the rays, where there are 

 papular pores, are similar to the median ones, but slightly smaller 

 and mostly notched for the papula. They are somewhat oblique 

 or one-sided. 



The papulae are in six rows on the rays ; others are on the disk. 

 The central dorsal pore is easily seen. The madreporic plate 

 has a small convex, round, grooved top, but the basal part is 

 considerably larger, with lobed margin, and has no gyri. 



The adambulacral plates have four very slender graded spines 

 in the marginal comb, and a close group of two, or sometimes 

 three larger ones, on the actinal surface. The interactinal plates 

 have mostly two or three small spinules. The apical peroral 

 spines are large and acute. Curacoa, No. 7469 (Nat. Mus. coll.). 



The color, in life, seems to be quite variable. At Bermuda, 

 where I found it common, adhering to the under side of large 

 flat masses of limestone, it was always of a pale, but distinct, 

 blue color. 



This small species is the most common shallow-water member 

 of the family, from the Florida Keys and reefs to the Lesser 

 Antilles and to the Bahamas and Bermudas. Curacoa (Yale 

 Mus. specimen described). Peirier (1876) recorded ten speci- 

 mens from Guadeloupe, among which one had four and another 

 six rays. The Bahama Expedition took it at the Tortugas (one 

 specimen was six-rayed), Jamaica (Clark). 



Bermuda, common under large stones. Old Providence (Yale 

 Mus.). 



The only closely related species is A. modesta Yerrill, from 



