440 PROCEEDINGS OF THE NATIONAL MUSEUM vol.89 



quite, straight ; petals I and V, 34 by 17 mm., widest at or very near 

 the tip and well open there. All petals blunt, the posterior pair 

 being almost truncate. Lunules II and IV about 18 mm. long by 

 3 mm. wide, nearly or quite straight although the posterior margin 

 may be concave; lunules I and V similar, a trifle shorter but about 

 the same width; unpaired lunule long and nearly straight, about 

 30 mm. long by 4.5 mm. wide, reaching to within 13 mm. of the disk 

 margin. Periproct about 4.5 mm, long by 2.5 mm. wide, its anterior 

 margin scarcely 4 mm. from the margin of tlie peristome, which is 

 about 4 mm. in diameter, rounded-pentagonal, the ambulacral knobs 

 on the margin relatively low and inconspicuous. Ambulacral fur- 

 rows of lower surface conspicuous, the intermediate areas in each 

 ambulacrum being notably wide; in II and IV these areas are 45 mm. 

 long and 24 mm. across where widest. 



Primary spines of dorsal surface less than 1 mm. long, very slender 

 and abruptly capitate ; but the heads are relatively small when com- 

 pared with those of M. lata; they are distinctly larger than in M. 

 quinqules'perforata. Surrounding the lunules and around the margin 

 of the test the primaries are 2-3 mm. long, flattened and blunt, 

 not at all capitate; around the lunules, particularly the unpaired 

 one, they are widened at the tip but not so conspicuously as in lata. 

 On the oral surface the primaries are as in other Mellitas, 3-4 mm. 

 long, very slinder, more or less horizontal in position, and arranged 

 so that in any given area they all point in the same direction. No 

 pedicellariae have been found. 



In color the holotype is light brown with a grayish tint abactinally, 

 more reddish brown on the oral surface. 



Locality. — Cumami, Venezuela ; Captain Couthouy, 1859. 



Holotype.— M.C.7u. No. 246. 



Notes. — There are two paratypes from Cumanii, but they are per- 

 fectly bare though not at all bleached; the larger is 94 by 109 by 

 10 mm., with tlie apex only about 30 mm. from the anterior margin; 

 the oral ambulacral area IV is 43 by 22 mm.; the color is brown, 

 with the aboral side unevenly tinted with violet or greenish. The 

 smaller specimen is 88 by 96 by 10 mm., Avith the apex about 35 mm. 

 back; oral ambulacral area IV is 41 by 24 nun., and the upper surface 

 has a distinctly greenish cast. 



There are additional paratypes in the Museum of Comparative 

 Zoology. One from Manzanilla Beach, east coast of Trinidad, 68 by 78 

 by 8 mm., has the apex a little more than 20 mm. back and the oral 

 ambulacral areas II and IV, 34 by 20 mm. ; the color above is dull 

 greenish, orally brown. From Mayaro Bay, east coast of Trinidad, 

 there are four small nearly bare specimens, one of which is notable 

 for its relatively long, narrow form, 57 by 63 mm. ; while the others 



