44 NATURAL HISTORY BULLETIN 



The dorsal surface is formed of openly reticulated plates, 

 leaving large sunken papular areas, containing groups of three 

 or four papulge. The investing dermis is thick. 



The dorsal, dorsolateral, and lateral spines are very small and 

 form about nine irregular rows, with scattered spines between 

 them. The marginals are not distinct. 



Besides the nine rows there is a regular row of interactinal 

 spines, which ceases at about midlength of the ray. The adam- 

 bulacral plates have a short, thick, obtuse furrow-spine, and ex- 

 terior to it, an equally larger but rather shorter spine; outside 

 of this there may be, in the same transverse line, one or more 

 small spines. 



Taken by the Blake at two stations among the Lesser Antilles, 

 in 120 to 123 fathoms, and in the Gulf of Mexico, off West Flor- 

 ida, in 101 fathoms. 



This has much smaller spines than specimens of E. spinulosus 

 of the same size, and the surface appears more areolated. 



Thyraster serpentarius (M. and Tr.) Ives. 



Eohinaster serpentarius M. and Tlosch., Syst. Ast., p. 24, 1842, Perrier, 



op. cit., vol. iv, p. 370, 1875. Lutken, op. cit., p. 285 [61], 1871. 

 Thyraster serpentarius Ives, op. cit., p. 329, pi. viii, figs. 19-21, 1890. 



The genus Thyraster, established for this species by Ives 

 (1890), is separated from Echinaster especially by the character 

 of the dorsal and marginal plates, which are quadrangular, or 

 rhombic, overlapping by their angles, and placed in regular 

 longitudinal rows. They bear three or four small, thorny spines, 

 in a row, on the distal edge. The adambulacral plates mostly 

 bear a row of three or four small spines on the distal margin, 

 with a small furrow-spinelet. The marginal plates usually have 

 three spines on the distal edge, rather larger than those of the 

 dorsal plates, but still quite small. Diameter of the type, 4 

 inches. 



It is a Mexican species, recorded by Miiller and Troschel, and 

 later by Ives and others, from Vera Cruz. 



Genus Henricia Gray, 



Henricia Gray, Ann. Mag. Nat. Hist., vi, p. 184, November, 1840; Synopsis 

 Starfishes, p. 5, 1866. Bell, Ann. and Mag. Nat. Hist., vi, p. 473, 1890; 



