302 THE VOYAGE OF H.M.S. CHALLENGER. 



Strait, 35 to 45 fathoms ; Caribbean Sea, abundant between 50 and 262 fathoms ; 

 off Cape Frio, Brazil, 35 to 45 fathoms (Hassler). 



Remarks. — This species has been figured for the sake of comparison with the other 

 ten-armed species of Actinometra which belong to the Solaris-group (PI. LII. 

 fio-s. 1, 2, 15). The essential difference between them is the absence in the Echinoptera- 

 oroup of the syzygies between the two outer radials and the two lower brachials 

 respectively, these joints being articulated as in most species of Antedon. 



The examples of this species obtained by the Challenger at Bahia were the first 

 representatives of the genus which I had seen from the Brazilian coast ; and as I could 

 not identify them with any form then described, I proposed to call the type Actinometra 

 brasiliensis. The calyx is figured under this name on PL IV., which was printed off 

 before I received the " Blake " collection containing the original examples of Actinometra 

 meridionalis, and also a very large series of variations on the same general type. The 

 exact number of specific forms belonging to this type which are represented in the 

 Caribbean Sea, is a point which I propose to work out in my "Blake" report; and for 

 the present therefore the Challenger species may be known under the name Actinometra 

 meridionalis, though it is quite possible that this may have to be discarded in favour of 

 Actinometra echinoptera, Mliller, sp. 



The dimorphism of the arms which is so common in the eastern forms of the genus 

 is very well marked in some of the Challenger specimens of Actinometra meridionalis, 

 the hinder arms being ungrooved and consisting of but half the number of joints wbich 

 occur in the anterior arms. But none of them possess the problematical "sense-organs" 

 on the pinnules which occur both in some individuals from Cape Frio and in others from 

 French Eeef on the Florida coast. 



The calyx is that of a very typical Actinometra. The centro-dorsal is small and 

 discoidal (PL IV. fig. 4a), and the articular faces of the radials are set vertically with 

 small muscle-plates, so that their ventral aspect shows a widely open central funnel 

 (fig. 4c) ; while there is a well-developed basal star, an isolated ray of which is shown in 

 PL IV. fig. 46. 



Actinometra, Series III. 



Two articulated distichals. 



Remarks. — This corresponds to Series III. of the Antedon-species, and comprises the 

 multibrachiate forms in which there are but two distichal joints united by a bifascial 

 articulation like that between the two outer radials. There may be no further division 

 as in Actinometra maculata, Actinometra simplex, and in some forms of Actinometra 

 pulchella (PI. LII. fig. 2; PL LV. fig. 2; PL LIX. fig. 1). But in other examples of 

 Actinometra pidchetta and in Actinometra stelligera there are palmar series like the 



