Fisher — Notes on the Systematic Position of Starfishes. 8 



ment of the actinal plates (these being essentially astropectinoid 

 in disposition), and in having patently double ampullse. It is best 

 considered as representing a separate subfamily of the Astro- 

 pectinidse, the Craspidasterinae (new name). 



MiMASTER AND Radiaster. — In respect to its systematic posi- 

 tion Mimaster Sladen has been a rather restless genus. Sladen 

 recognized its curious combination of apparently incompatible 

 characters and made it the type of a subfamily of the Penta- 

 gonasteridse. It has been variously regarded as belonging to 

 the Archasteridae (Perrier, 1894), Plutonasteridse (Verrill, 

 1899), and Goniasteridas (Fisher, 1911), until recently it was 

 dignified by being raised to family rank (Verrill, 1914). Pro- 

 fessor Verrill 's disposition seems to be the best way out of the 

 difficulty. 



Since the publication of the "Asteroidea of the North Pacific" 

 I have had the opportunity of examining two true Mimasters, 

 M. tizardi Sladen, and M. notabilus Fisher, as well as the M. 

 cognatus of Sladen, which appears to be generically distinct. 



The abactinal skeleton of Mimaster is strongly astropectinoid, 

 the plates being typical penicillate paxillae, but the marginals, 

 while perhaps neutral, remind one strongly of the marginals of 

 Cycethra, a resemblance heightened by the actinal and adambu- 

 lacral armature, which is decidedly ganeriid. By having defi- 

 nite sucking disks on the tube feet Mimaster is removed from 

 proximity to Leptychaster, an association suggested by the dorsal 

 surface, including the marginals, while it can not be placed in 

 the Ganeriidse because it possesses superambulacral plates and 

 lacks the heavily calcified internal interbrachial pillar, the 

 reticulated, imbricated, abactinal skeleton, and the asterinoid 

 abactinal armature of Cycethra and Ganeria. 



In Mimaster the membranous interradial septum forms a com- 

 plete partition from the side wall of the disk to a free margin 

 close against the stomach; but in Cycethra and in Ganeria (as 

 in Solaster and in Asterina) there is a rigid pillar running from 

 above the mouth plates to the abactinal surface, the coelom 

 being undivided between this pillar and the margin (an incom- 

 plete calcified septum). 



In this connection I would like to call attention to the resem- 

 blance between Ganeria and the Solasteridse, recently suggested 



