4 Proceedings of the Biological Society of Washington. 



in conversation, by Mr. A. H. Clark. The marginal plates of 

 Ganeria falklandica are essentially like those of Solaster, and in 

 the adambulacral armature we find a very generalized form of 

 the peculiar pectinate type of the Solasteridffi. The form and 

 armature of the mouth plates, the actinal intermediate plates, 

 and even the adambulacral plates can, however, be more nearly 

 matched in the Asterinidse. The abactinal skeleton, though of 

 on open reticulate form, especially on the disk, is more nearly 

 like that of the Asterinidae than like that of the Solasteridse. 



While perhaps in some way related to the Ganeriidse, I think 

 Mimaster is well within the Phanerozonia. Gephyreaster, which 

 I formerly associated with it in the Mimasterinse, is probably 

 more nearly related to Pseudarchaster . Unless its resemblance 

 to Mimaster is only superficial, it may constitute an annectant 

 group. 



The purely nomenclatorial side of the matter is complicated 

 by Radiaster elegans Perrier. Through the kindness of Dr. H. L. 

 Clark I recently examined the type (unfortunately dried) in 

 the Museum of Comparative Zoology (No. 909, Dominica, West 

 Indies, 982 fathoms). From every outward indication this 

 species is a typical Mimaster. Radiaster* has one year priority. 

 The family and its two genera may be summarized as follows: 



Radiasteridce, new name. 



Mimasteridae Verrill, Monograph of the Shallow- Water Starfishes of the 

 North Pacific Coast, 1914, p. 282. 



Characters. — Phanerozonia with small, subeqnal, snbpaxiUiform mar- 

 ginals, resembling the Astropectinidfe abactinally and the Ganeriidae 

 actinally, but with sucking disks on tlie tube feet and complete mem- 

 braneous interbrachial septa, and superambulacral plates; abactinal 

 skeleton consisting of penicillate, usually independent, paxillae; actinal 

 plates imbricated in transverse series, tabulate, with a coordinated tuft of 

 spinelets ; adambulacral armature a coordinated tuft of spinelets increasing 

 in length toward the two or three almost undifferentiated furrow spinelets ; 

 first adambulacral somewhat compressed; mouth plates rather astro- 

 pectinoid, with a straight marginal series of spines and without an un- 

 paired median spine at the inner angle ; madreporic body covered with 

 paxillae springing from its surface. 



Synopsis of the Component Genera. 



1. Gonads confined to the disk and consisting of several tufts springing 



from a common point close to the interbrachial septum ; hepatic 



• Radiaster Perrier, Bulletin Museum Comparative Zoology. Vol. 9, June, 1881 p. 17. 

 Mimaster Sladen, Proc. Royal Soc. Edinburgh, Vol. 11, 1882, p. 579. 



