Verrill, JVbtes on JRadiata. 295 



ter of the actinal area, not including aetinal cuts, I'lO; extreme 

 diameter, including cuts, 1-25 ; of abactinal area "3; longest spines 

 about 5 inches in length, '07 in diameter. 



This species is allied to D. Antillarum Phil, of Aspinwall and the 

 West Indies, but may be at once distinguished by its much larger 

 actinal area, as compared to the abactinal area, or to the diameter of 

 the test. In D. Mexicana the jjrojiortion of the actinal area to the 

 diameter of the test is about 1 : 2*05, in D. Antillarum as 1:2-3. In 

 D. Mexicana the large tubercles of the outer interambulacral roAvs 

 continue nearly to the ovarial plates, diminishing but little in size, 

 and there is less space, also, above the median rows than in the other 

 species. 



The sutures between the interambulacral plates are rather deep 

 and well marked. The spines are very long and sharp, about twice 

 as long as the diameter of the test. 



Color of the dried specimen brownish black, spines black. Young 

 specimens about half an inch in diameter, from Cape St. Lucas, have the 

 spines regularly banded with deep purple alternating with purplish 

 white. 



Echinodiadema, gen. nov. 



Test depressed, circular. Actinal cuts slight. Buccal membrane 

 with five principal groups of oblong scales, bearing numerous slender 

 spines and pedicellarire. Ambulacral pores trigeminate, the poriferous 

 zones wider beneath, where the rows of three pairs are more trans- 

 verse. Tubercles arranged much as in Diadema, — two principal rows 

 in the ambulacra, and four in the interambulacra, of which the exter- 

 nal ones are smaller and border the poriferous zones. Anal membrane 

 small, covered with small scales. Spines long, slender, hollow, exter- 

 nally resembling those of Diadema. 



Echinodiadema coronata Vemii, sp. nov. 



Test circular, much depressed, actinal opening one half the diam- 

 eter of test, with very slight cuts, its membrane partially covered by 

 five principal groups of large oblong scales, which support numerous 

 slender, somewhat clavate spines, •! inch long, and numerous short, 

 rounded pedicell arias. Ambulacral pores large, in arcs of three pairs, 

 becoming more oblique below, where the zones are wider ; tubercles 

 in two rows, rather large, with a median zigzag line of miliaries. 

 Interambulacra about twice as wide as the ambulacra, with two rows 

 of tubercles, somewhat larger than those of the ambulacra, reaching 

 the abactinal region ; external to these are two irregular rows of small 

 tubercles bordering the ambulaci-a ; and between them two imperfect 



Trans. Connecticut Acad., Vol. I. 38 June, ] 867. 



