ECHINOMETRA SUBANGULARIS. 283 



Echinometra subangularis 



! Ciduris subangularis Leske, 17 78. Kl. Adclit. 

 '.Echinometra subangularis Desml. 1837. Syn., p. 266. 



PL X". f. %, 3, 4. 



Poriferous zone broad ; pores arranged in arcs of not more than seven 

 pairs, usually six ; pores of a pair large, distant ; abactinal system narrow ; 

 madreporic genital far exceeds in size the other genital plates, which are 

 small, with large genital openings. What is specially remarkable in the 

 West India species is the great size of the auricles, extending in a T-shaped 

 broad column half-way the length of the polar axis, connected by a robust 

 ridge at base, equalling in height one third of the auricles. Auricular arch 

 small. Actinostome large and pentagonal ; the number of coronal plates of am- 

 bulacra in young specimens is materially greater than in the interambulacra, 

 but older specimens do not show a striking difference in the size of the 

 primary tubercles of the two areas. The variation in proportion of the test, 

 the structure of the ambulacra near the actinostome (more or less petaloid), 

 the proportions of the spines and the test, are so great that it is only by ex- 

 amining a large series of specimens that good characters, which are but few, 

 can be enumerated to distinguish this from the other species of Echinometra. 



The color of the spines varies greatly from a dark violet-green to a deep 

 violet almost black. With increasing age, as the test becomes more gibbous, 

 the coronal plates increase greatly in size, and the primary vertical rows of 

 tubercles often attain an extraordinary size, which has caused them, when 

 flattened, to be mistaken for genuine Stomopneustes. 



From an examination of typical specimens of Echinus lucunter Lam. it 

 became evident that Lamarck's species was the common Echinometra, hav- 

 ing such an extensive range in the Pacific and Indian Oceans ; extending 

 from the Sandwich Islands to the Red Sea. It was with some doubt, how- 

 ever, that the name Michelini was adopted in the Museum Bulletin for our 

 common West India species, the varieties of which have served as the type 

 of many species : the large, somewhat oblong, swollen-sided adult, with short 



