20 MR. P. IT. CAEPEKTEE ON THE GENUS ACTINOMETEA. 



a terminal comb. These two characters, however, do not always coexist; for Pourtales ' 

 describes Antedon meridionalis, A. Ag., as having an excentric mouth, while he says 

 nothing about the first pinnule, except that it is "rather long, the first five or six joints 

 webbed by the perisome." 



Again, in many of the Comutuloi Avith an excentric mouth which I have examined, 

 the terminal comb is not limited to the oral pinnules only, but may occur at intervals on 

 different pinnules till near the end of the arms, although it is uevcr so well developed as 

 it is on their basal or oral pinnules, fewer of the terminal segments bearing the processes 

 which go to make up the comb. 



Lov6n- has found the same to be the case in the new Comatula which he has descrilied 

 under the name of Plianorjcuia tiipica. Speaking of the pinnules, he says, on p. 232 : — 

 "In nonuuUis (omnil)us ?) avticuliS 1. 9 ultimi convoluti, pcctinati, margine cujusvis ex- 

 terno in laminam lanceolatam magnam erectam producto ;" but he goes on to say (p. 233), 

 " Os centrale. Tubus analis crassus in media area interradiali. Sulci tentaculiferi fere 

 qualcs in Aniedone." 



Here, therefore, a terminal comb on the pinnules coexists with a central mouth ; so 

 that all the four possible variations may occur of these two characters, viz. the position of 

 the mouth and the condition of the terminal segments of the pinnules. 



Thus Antedon rosacea &c. have a ccutral mouth and no comb. 

 „ Phanogenia typica has a central „ and comb. 



„ Actinomeirasolarisk.c.\ia.\'ea.xie\ccntx\c „ and conil). 

 „ Comatula meridionalis lias an excentric „ and no comb. 



Leaving Thaiiogenla out of consideration for the present, as it was unknown to 

 Johannes Miiller, the following scheme will rejiresent the relations oi Antedon anHAeti' 

 nometra as used by Dr. Liitken and myself, to Alecto and Actinometra as used by 

 Miiller : — 



Alecto. Ambulacra .symmotriciilly 1 nioudi central. Antedon. Oral innnules not special])" 



distributed on tbo disk. J mouth excentric. "^| distinguished. 



Actinometra. Ambulacra unsymmctri- ] ('Actinometra. Oral pinnules nearly 



cally distributed on Ihe I moulh excentric. | always have a ter- 



disk. j J minal comb. 



(§ 15) We arc noAv in a position to investigate which species of the numerous Coma- 

 ttilcB described by Midler can be referred to Actinometra under its ncAv definition, and 

 what further subdivisions of the genus are possible according to the principles of classi- 

 fication introduced by ]\I idler. Before doing so, however, it will be advisable to devote 

 a little time to a consideration of the descriptive terminology which he employed, and 

 of the manner in which it has been modified by later writers. 



In Fentacrifius and C'omattUa Miiller regarded the arms as starting directly from the 

 five radial axillaries. The two primary arms borne by each of these might either remain 



' Loc. cit. No. 11, p. 3.55. Pourtales hero evidently uses Antedon as equivalent to Alecto, and not in the sense in 

 ■which it was employed by Mr. Norman, viz. to designate those forms only in which the mouth is central (or nearly 

 so) and the anus lateral. To avoid confusion, 1 shall speak of this species simply as Comatula meridionalis. 



' " Phanogenia, ett hittills okiindt sliigtc af fria Crinoidcer," Cfver. af Kongl. Vetcnsk.-Akad. Fiirhandl. 186G, 

 No. 0, p. 223. 



