76 SCHIZASTEK OKBIGNYANUS. 



* Schizaster orbignyanus A. Ac 



Schizaster orbignyanus A. Ag. Bull. M. C. Z., YIIL, No. 2, p. S4, 1880. 

 Lesser Antilles. iU-10ii7 fathoms. 



PL XXVIII. Fig*. 1-7. 



This species extends as far north as the New England coast, specimens 

 having been dredged by the United States Fish Commission off Martha's 

 Vineyard in 100 and 130 fathoms. They differ very considerably from the 

 specimens dredged by the Blake in the Eastern Caribbean. The northern 

 specimens, while retaining the characteristic outline of those from the Carib- 

 bean, yet differ from them in having a much broader peripetalous fasciole, 

 more like that of S. canuliferus ; the northern and southern specimens, again, 

 agree in the great width of the actinal plastron at the posterior extremity, 

 and the small size of the anal system as compared with that of S. cana- 

 liferus, and are covered by a closer tuberculatum also, a character which 

 readily distinguishes the specimens of the two species thus far compared. 

 The test from the lower side of the anal system to the edge of the actinal 

 plastron is more bevelled than in S. canaliferus. In the few specimens ot 

 S. orbignyanus I have had occasion to examine, the lateral and anal fascioles 

 vary greatly in distinctness. In the Caribbean specimens the lateral fasciole 

 extends continuously along the sides of the test to the level of the side of 

 the anal system, and there forms a sharp, well-defined triangular anal fasciole. 

 In the northern specimens the lateral fasciole is often indistinct or disappears 

 entirely, only the anal fasciole remaining. It is interesting to note that, in 

 the specimens of S.fragiKs dredged off our eastern coast, the anal fasciole 

 disappears fust, leaving only a part of the lateral fasciole extending from the 

 peripetalous fasciole towards the anal system. The peripetalous fascioles 

 are of a dark violet color, forming a strong contrast to I he greenish yellow 

 spines with silvery lustre which cover the upper part of the test. The lateral 

 and anal fascioles can scarcely be distinguished by their color from the spines 

 of the actinal side and those towards the ambitus, which with the exception 

 of the spatula-shaped spines of the actinal plastron are of a darker color than 

 those of the nbactinal side of the test, and within the peripetalous fasciole. 



Whether the differences here noted between S. canaliferus and S. orbigny- 

 anus are merely local or more important, comparisons of more extensive series 

 of these species alone can determine. 



