BEISSOPSIS LYIIIFEKA. 69 
of a subgenus of Rhinobrissus, which will hold to it very much the same 
relation which Periaster holds to the true Schizaster. It will represent the 
embryonic stage of Rhinobrissus and recall to us the earliest true Spatangoid 
genera of the Chalk still having ambulacra nearly flush with the test, with a " ^ 
well-developed subanal and a rudimentary peripetalous fasciolc. . ,yyj'^^^^^^ 
Brissopsis lyrifera Agass. 
Lesser Antilles, off Havana. Lat. 28° 51' 30" N., Long. 89° 1' 30" AV. OH" tlie mouth of the 
Mississippi. Lat. 41° 29' 4.5" N., Long. 65° 47' 10" W. 118-1394 fathoms. f 
For list of Stations, see Bull. M. C. Z., VIII., No. 2, p. 83, 1880. ~- 
PI. XXVI. Figs. 7-18. 
Brissopsis lyrifera appears to be one of the most widely distributed species 
of the Atlantic fauna, and is also found in the Caribbean and in the Gulf of 
Mexico. 
I have already, in the Revision of the Echini (p. 354), spoken of the 
great variation I had observed in the course of the petaloid ambulacra of 
this sj^ecies, as well as of the variations found in the subaiial fasciole. An 
extensive series of specimens of this species has now been brought together 
by the dredging of the Blake. Tliesc throw additional light on the changes 
we may expect to find among Spatangoids of this group in one and the 
same species. I had already observed considerable dilierence in the outline 
of the test. Specimens dredged off the mouth of the Mississippi were 
generally quite globular, and presented the extreme form in that direc- 
tion, while the specimens collected along the east coast of the United 
States as far north as George's Bank, and in the Eastern Caribbean and 
the Straits of Florida, although varying considerably in outline, yet pre- 
sented no very marked differences except such as we have seen were due 
to growth, and agreed on the whole quite well with the specimens of 
Brissopsis known from other parts of the North and South Atlantic. Be- 
tween Jamaica and San Domingo there were dredged three specimens of 
Brissopsis representing the extreme elongated form, with an anteriorly 
bevelled flat surface, at the abactinal extremity of which is situated the anal 
system. These specimens were further characterized by an exceedingly well 
defined subanal fasciole, with an indistinct anal fasciole extending to the 
posterior part of the peripetalous fasciole. As mentioned in the Revision of 
the Echini, the subanal fasciole is quite variable ; in many cases the anal 
