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



During the winter of 1875-76 circumstances enabled me to examine the numerous 

 Comatulse which had been collected by Professor Semper among the Philippine Islands 

 some years before. Among them were a dozen examples of one common species, together 

 with several other well-defined types ; and I was soon led to conclude, as Liitken had 

 previously done, though unknown to me, that the essential difference between Antedon 

 and Actinometra depends upon the position of the mouth and not upon the number of 

 ambulacra reaching the peristome. In reply to the inquiries which I addressed to him 

 upon the subject, Dr. Liitken was good enough to communicate to me his own observa- 

 tions, and also his discovery of the constant presence of a terminal comb on the lower 

 pinnules of exocyclic Comatulse. A few months later, by the kindness of Professor 

 Perrier, I was enabled to verify Liitken's conclusion for myself on the fine collection of 

 Comatulse in the Paris Museum ; while at the same time I succeeded in making out 

 various other points of difference between Antedon and Actinometra, and referred seven- 

 teen of the Comatu Za-species then known to the latter genus. 1 



A subsequent study of the large collections obtained by the Challenger, the " Alert," 

 and the " Blake," and also of the Comatulse in the principal museums of the continent, 

 has afforded ample verification of the earlier conclusions which had been reached by Dr. 

 Liitken and myself; and it has likewise enabled me to make out some other distinctive 

 characters both of Antedon and of Actinometra. 



The genus Phanogenia was established by Loven 2 in 1866, for a remarkable 

 Comatula from Singapore which has a stellate centro-dorsal bearing but slight traces 

 of cirri, a nearly central mouth, and a terminal comb on the lower pinnules. Several 

 examples of Actinometra of different species, with a centro-dorsal like that of Phanogenia, 

 were dredged by the Challenger (PL LVII. fig. 1 ; PI. LXIII. fig. 6 ; PL LXV. figs. 1-6 ; 

 PL LXVII. fig. 1 ) ; and I have seen others in different museums, many of them with the 

 mouth unusually near the centre of the disk, and the ambulacra almost as uniformly 

 distributed as in Antedon ; but the interpalmar area containing the anal tube is always 

 considerably larger than its fellows. This is also the case in Loven's original specimens 

 of Phanogenia, which I therefore referred to Actinometra in 1882, s for it became no 

 longer possible to distinguish Phanogenia as a separate genus by the characters of its 

 centro-dorsal only, as I have pointed out on pp. 13-16. 



Remarks. — In by far the greater number of individuals which belong to the genus 

 Actinometra the mouth is situated at some distance from the centre of the disk, which 

 is occupied by the anal tube, and it is occasionally very close to the margin (PL LVII. 

 fig. 3; PL LXII. fig. 4; PL LXIV. fig. 2; PL LXVIII. fig. 1 ; see also Part I., pi. lv. 

 fig. 2 ; pi. lvi. figs. 7, 8). The peristome is usually fairly open and somewhat elongated 



1 Trans. Linn. Soc. Lond. (Zool.), ser. 2, 1879, vol. ii. p. 27. 

 - Ofversigt h. Vetensk. Ahad. Forhandl., 1866, No. 9, p. 231. 

 3 Notes from the Leyden Museum, 1882, vol. iii. p. 195. 



