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



Two of the rays only are preserved, the three others having broken away above the 

 radial axillaries. One of them seems to have been of much smaller size than the rest, to 

 judge from the two joints of it which remain (PL LVI. fig. 3). I am not sure, however, 

 that this is simply a case of regeneration from the primary radials. For the small first 

 radial in this case differs somewhat from its fellows ; and its flattened central portion, 

 which bears the small second radial, projects outwards a little beyond the general line of 

 the radial pentagon. There may be some meaning in this asymmetry ; but as the disk is 

 lost it is impossible to determine whether it is related in any way to the position of the 

 anus. 



The character of the union between the first two distichals of this type has puzzled 

 me greatly. It has very much the appearance of a syzygy, but I have not liked to attempt 

 to settle the point by an actual examination of the joint-faces, as it would have involved so 

 much further mutilation of an already imperfect specimen. This has been possible, how- 

 ever, in Actinometra typica, which has the usual bifascial articulation between the first 

 two distichals ; and as there are so many points of resemblance between this species and 

 Actinometra rnultibrachiata, it is by no means improbable that the latter may be in the 

 same condition, though the external characters seem to indicate the presence of a syzygy. 

 This would be a new type of structure altogether ; though it occurs abnormally in the 

 distal parts of the rays of Actinometra typica (PI. LVII. fig. l), as I have already 

 pointed out. 



For the present, therefore, it will be safer to leave Actinometra rnultibrachiata in the 

 same group with Actinometra typica, until the question can be definitely settled by the 

 examination of more material. 



Actinometra, Series II. 



The two outer radials articulated. Ten arms. 



Remarks. — This is a small series and contains but one group, which may be called 

 the Echmoptera-growp, after the name of its first described species. The Mullerian type 

 of this species is in the University Museum at Berlin, where it was deposited by Captain 

 Wendt many years ago, though no locality was recorded for it. I was permitted to 

 examine it in 1880, and have since come to the conclusion that it is a Caribbean species, 

 and not improbably identical with one of the many variations of the type which was 

 described by Pourtales in 1869 under the name Antedon meridionalis, A. Agassiz, MS., 

 from the coast of South Carolina. This conclusion is strengthened by the fact, for which 

 I am indebted to the kindness of Professor E. von Martens, that the Berlin Museum also 

 contains some other Caribbean Echinoderms which were deposited by Captain Wendt. 



Three of the five remaining species of the Echinop>tera-gvou^ are also members of 

 the Caribbean fauna, viz., Actinometra pulchella, Pourtales, sp., Actinometra rubiginosa, 



