REPORT ON THE ASTEROIDEA. 593 



I have added a new genus, Colpaster, for the reception of a form characterised by the 

 presence of an externally conspicuous azygos interradial plate separating the first pair 

 of adanibulacral plates, and further differing from Freyella in the development of the 

 armature of the mouth-plates .and the adambulacral plates. . 



Since the discovery of Brisinga endecacnemos in 1853, perhaps no other Asterid has 

 been looked upon with so much interest "by naturalists, or "has "given rise to a greater 

 amount of speculation as to its antiquity and structural relations. The Brisingidae have 

 been stated to represent the most primitive type of living starfishes, and to present a closer 

 approach to the Ophiuroidea than any other form. I consider that these views are entirely 

 unwarranted. It is now generally admitted by all workers at the group that the Brisin- 

 gidae are most nearly related to the Asteriidae, Heliasteridae, and Echinasteridse. Taking 

 Asterias as a comparatively well-known and central form, it may be asked, Does the plan 

 of structure of this genus represent the most archaic or the most primitive type of Asterid 

 structure with which we are acquainted'? and, Does it present the nearest approach to the 

 plan of Ophiuroid structure ? The reply to these questions would, I think, be unhesita- 

 tingly in the negative. Supposing for the sake of argument that the Brisingidae are older 

 than the Asteriidae, May Asterias be considered to represent even a penultimate stage 1 I 

 think not, and in my opinion such an assumption would be entirely without foundation. 

 Palaeontological evidence certainly does not support it, and the embryological history 

 of Asterias points unequivocally to a phanerozonate ancestry. In my opinion the 

 Brisingidae are true cryptozonate Asterids, very nearly related to the Asteriidae, Pedicell- 

 asteridae, Heliasteridae, and Echinasteridae, and probably derived from a common ancestor, 

 the divergence of form and the peculiarities of structure now exhibited by Brisinga being 

 the result of modification produced by the extreme isolation and the exigencies of the 

 abyssal depths in which the family has existed. We know too little of the embryology 

 of Brisinga and its allies to speculate further at present on its antiquity or relations, 

 and to say more than is suggested above in our present state of knowledge would be, in 

 my opinion, to ignore altogether the evidence of palaeontology and of the embryological 

 development of those forms with which we are acquainted. 



Synopsis of the Genera included in the Family Brisingidae. 



A. Disk large. Rays very numerous. Abactinal plating reticulate. Forficiform 



and forcipiform pedicellariae present ....... Labidiader. 



B. Disk small. Rays not very numerous (six to seventeen in number). Abactinal 



plating when present not reticulate. No forficiform pedicellaria?, forci- 

 piform pedicellariae very numerous. 

 a. Abactinal plating consisting of narrow widely-spaced transverse bands or 

 ridges limited to the basal portion of the ray. 

 a. Intermediate abactinal membrane punctured by papulae . . . Odinia. 



(zool. CHALL. EXP. — rAUT li. — 1888.) 71 



