BEISSOPSIS LYRIFERA. 



of a subgenus of Rhinobrissus, which will hold to ii very much the same 

 relation which Periaster holds to the true Schizaster. It will represenl the 

 embryonic Btage of Rhinobrissus and recall to us the earliesl true Spatangoid 

 genera of the Chalk still having ambulacra nearly Bush with the test, with a 

 well-developed subanal and a rudimentary peripetalous fasciole. 



Brisscpsis lyrifera \ 



I, i r Antilles, ofl !! i 51' 30" X.I Ofl the m 



issippi. Lat. II 29' 15" N.. I - 65° 47' 10" ms. 



Foi i. BulL M i'. / , VIII., No. 2, p. B3, I--". 



/v. XXVI. Figs. 7-18. 



I: wpsis lyrifera appears to be one of the mosl widely distributed species 

 of the Atlantic fauna, and is also found in the Caribbean and in the Gulf of 



Mexico. 



1 have already, in the Revision of the Echini (p. 354), spoken of the 

 greal variation I had observed in the course of the petaloid ambulacra of 



this species, as well as of the variations found in the subanal fasciole. An 



extensive series of specimens of this species has now been broughl together 

 li\ the dredging of the Blake. These throw additional light on the changes 

 we may expect to find anion-- Spataugoids of this group in one and the 

 same species. I had already observed considerable difference 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 easl coast of the Dnited 

 Slates 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 Hat 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 Bubanal fasciole is quite variable; in many cases the anal 



