302 Verrill, N'otes on Radiata. 



plates each with a group of small, unequal tubercles. Abactinal area 

 small, closed by five principal plates of unequal size. 



Color of spines, on a specimen dried from alcohol, bright purple, test 

 light purple with yellowish white bands extending fi-om the actinal 

 area along the poriferous zones and covering the adjacent tubercles as 

 far as the outer curvature of the sides, forming thus a ten-rayed star. 

 An undefined space around the ocular and genital plates is also yel" 

 lowish white. A narrow black ring surrounds the teeth. Diameter 

 of the largest specimens about one inch. 



Cape St. Lucas, Cal., — J. Xantus, (Smithsonian Institution). 



LytecllinUS A. Agassiz, Bulletin Mus. Comp. Zool., p. 24, 1863. 

 Hemiechinus {pars) Girard, MS. (Coll. Smithsonian Inst). 

 Psilechinus Liitken, Bidrag til Kunskab cm Echin., p. 25, 1864 



This genus agrees with Psanimechhncs in having the pores in ob- 

 lique rows of three pairs, and in the scales of the buccal membrane, 

 but differs in having deeper actinal cuts, with thickened, or sometimes 

 revolute, edges ; and in having partially naked median spaces on the 

 upper part of the ambnlaeral and interambulacral zones. The species 

 also attain a much greater size than is usual in Fsammechinits. 



The Echinus variegatus may be regarded as the type. In the 

 Smithsonian Institution there are specimens of X. Carolinus Ag, 

 under the name of Semiechimis nohilis Girard MS., but I cannot find 

 that such a genus has ever been published. 



Lytechinus roseus Ven-iii, 



Boletia rosea A. Agassiz, op. cit., p. 24. 



Numerous large specimens of this fine species were dredged in 

 Panama Bay, in 6 to 8 fathoms, shelly bottom, by Mr. Bradley. Mr. 

 Agassiz described specimens from Aca})ulco. 



The largest specimen has a test 3 '6 inches in diameter; I'S high; 

 diameter of actinal opening, not including cuts, 1'25 ; depth of cuts 

 •27 ; from outside of madreporic plate to outer edge of opposite ocular 

 plate "52 ; diameter of anal membrane "2 ; length of longest spines '5. 



Test thin, fragile, low, subconical, lower side concave, outline some- 

 what })entagonal. The ambulacral zones are two thirds as wide as 

 the interambulacral, and slightly raised above them, wdth a narrow, 

 somewhat sunken, median naked space on the upper side. On the 

 lower side there are six rows of ambulacral tubercles, which diminish 

 in size upward, the outside rows attaining the summit, the others 

 ceasing successively sooner. Interambulacral tubercles on the lower 

 side in ten rows, subequal in size ; the third row from each margin 



