36 NATURAL HISTORY BULLETIN 



spines are conical, acute, mostly isolated, sometimes in small 

 groups. 



Upper and lower marginal plates are not very distinct, with 

 spines like the dorsals. Adambulacral spines form a small oblique 

 or transverse row of two to four; the inner ones are smaller, 

 inserted in the groove, just above the margin. 



The genus Othilia Gray, December, 1840, appears to be a syno- 

 nym of Echmaster Miiller and Troschel, April, 1840. The type 

 of the latter was E. spinosus ^ = A. echinophora Lam., both by 

 virtual tautology and by designation. (See foot-note in Miiller 

 and Troschel, Syst. Ast., p. 22, 1842.) Echmaster of Gray, 1866, 

 is AcantTimter of later writers. 



This genus is found in all tropical and subtropical seas, chief- 

 ly in shallow water. 



EcHiNASTER SENTus (Say) Liitkeu. 



Asterias sentus Say, Journ. Philad. Acad., v, p. 143, 1825. 



Othilia aculeata Gray, Annals Nat. Hist., vi, p. 281, 1840; Gray, Synopsis 



Starfish, p. 12, 1866. 

 Echinaster spinosus (pars) Miiller and Trosch., Syst. Ast., p. 22, 1842. 



Verrill, Notes on Eadiata, p. 343, 1867. Ives, Proc. Acad. Nat. Sci. 



Philad., for 1890, p. 325. Clark, Echinoids and Asteroids of Jamaica, 



p. 6, 1898. 



Othilia spinosa Agassiz,. Bull. Mus. Comp. ZooL, p. 308, 1869. 



EcMnaster sentus (Verrill, MSS., 1866). Liitken, Vid. Meddel., pp. 60, 



[284], 1871; 9 Perrier, Arch. Zool. Exper., iv, p. 366,, 1875; A. Agassiz. 

 North American Starfishes, p. 97, pi. x, figs. 1-6, 1877 (figs, of living 



and structure.) E. Bathbun, Echinoderms of Brazil, p. 147, 1879. 



Plate xxix; figure 2. Young. 



The two marginal rows of plates are pretty regular but not 

 much differentiated from the others in size or form. The upper 

 row usually has only one stout conical spine, with a mammiform 

 base, on each plate. It turns upward proximally, reaching the 

 dorsal side, and leaving a wide interradial intermarginal area, 

 in which there are a number of spineless plates, and usually one 

 short intermarginal row of plates bearing one spine each in a 

 typical specimen from Florida. 



8 The name spinosus (Eetz.) is not tenable for any species of the genus 

 for Asterias spinosa E. was antedated by A. spinosa Pennant, 1777. 



9 Liitken here refers to Verrill (correspondence) and to his determina- 

 tion in 1866 (op. cit., p. 348), of sentus. 



