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



When I re-described Actinometra Solaris in 1882, I added a diagnosis 1 of the form 

 which had been long known in the catalogues of the Godeffroy Museum as Actinometra 

 robusta, Liitken, MS. The chief character distinguishing it from Actinometra Solaris, 

 apart from its generally more robust nature, seemed to me to be the entire absence of 

 any expanded keels on the lower joints of its second and third pairs of pinnules. The 

 examination of the " Alert " collection has shown, however, that this distinction will no 

 longer hold good. The " Alert " dredged large specimens at Prince of Wales Channel, 

 Port Molle, and Port Curtis, which are indistinguishable from Actinometra robusta in 

 almost every other character but those of the lower pinnules. All of them have three, 

 and that from Port Molle as many as five pinnules with keeled basal joints ; and for 

 reasons which will appear immediately, we have, I think, no other course open to us but to 

 refer them all, together with Actinometra robusta, to one and the same type, Actinometra 

 Solaris. When describing the Comatulse obtained by the "Alert," Bell proposed, in the 

 following terms, 2 to establish a new species, Actinometra intermedia: — "As Mr. 

 Carpenter has pointed out, it appears to be possible, in part at any rate, to distinguish 

 A. Solaris from A. robusta by the character of the keels, which, in the former, are so 

 strikingly developed on the basal joints of the second pinnule. Basing myself on the 

 theory that the keel is constantly present on the basal joints of the second pinnule of 

 A. Solaris, and that it is never found on those of A. robusta, I venture to think that, in 

 the case of A. intermedia, we have to do with a form in which constantly the keels are 

 never as well developed as in A. Solaris, and never so slightly as in A. robusta, while at 

 the same time there are considerable differences in the extent of the development of the 

 keel, not only within the limits of the species, but even of the individual." 



I have made a careful examination of the half dozen specimens which Bell referred 

 to Actinometra intermedia, and I find it impossible to differentiate them from Actino- 

 metra Solaris. They present a great amount of variation in the carination of the basal 

 pinnules, but not more so than I have found in a number of specimens collected by the 

 Challenger in Torres Strait, which I now refer to Actinometra Solaris, though, like 

 Bell, I formerly considered them as representing a new species (which I called Actino- 

 metra strota), intermediate between Actinometra Solaris and Actinometra robusta. 

 The Challenger specimens from Booby Island and Albany Island, and Bell's Actinometra 

 intermedia from the latter locality, agree in every respect except colour. The lower 

 pinnules are sometimes almost as slightly keeled as in the ?'obusta-form (PI. LIU. 

 figs. 3-6); while, on the other hand, they may have all the characters of the pinnules in 

 the typical Actinometra Solaris (PI. LIU. figs. 9-12), and the development of the keel 

 is not constant in any individual specimen. They all agree, however, in having from 

 eighteen to twenty cirrus-joints, and in the indistinct nature of the medio-dorsal ridge ; 



1 Journ. Linn. Soc. Lond. (Zool.), 1882, vol. xvi. p. 517. 

 ! "Alert" Report, p. 166. 



