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



are considerably produced towards the dorsal side ; but in other individuals from these 

 and from other localities this character is entirely absent. That obtained by the 

 Challenger at Simon's Bay seems to have just liberated its ova, as a small group of them 

 is collected on the distal side of each genital pinnule, in the angle between it and the 

 arm (PL LXI. fig. 7). 



In nearly all the examples of this species which I have seen the mouth is very 

 distinctly interradial, as is well shown in Midler's diagram of Comatula icahlbergii, 1 and 

 in my own figures of Actinometra polymorpha. 2 In one or two cases, however, the 

 A ambulacrum is somewhat displaced forwards, though never so much so as to cause 

 the mouth to become radial. 



The disk is generally naked, but the neighbourhood of the anal tube sometimes bears 

 scattered granules ; while in one individual from Torres Strait there is a tolerably close 

 pavement of minute scale-like plates over the whole disk. The perisome of the arms 

 and pinnules in this individual is considerably reduced, and the genital glands are but 

 poorly developed, though in another from the same station, which was presented by Sir 

 AVyville Thomson to the Stockholm Museum, the perisome is much more substantial 

 and the genital pinnules, especially in the posterior arms, are much swollen, so that the 

 two forms differ greatly in their external appearance. 



Actinometra parvicirra, as described above, is a somewhat comprehensive type, 

 embracing as it does three of Midler's species, together with four others which have been 

 regarded as distinct at various times ; and its distribution therefore is considerably 

 extensive. It occurs to a distance of about 35° on either side of the equator, and has a 

 range in longitude of some 260° from the Cape of Good Hope to Peru. Long since 

 known from Natal, Timor, and from the Friendly Islands, it has subsequently been 

 discovered at numerous intermediate localities, such as Ceylon, the Moluccas, Phdippines, 

 Japan, Fiji, and East Australia ; and I quite expect that it will be eventually found in 

 the Atlantic, more especially as the species of Actinometra characteristic of that ocean 

 seems also to occur in the Arafura Sea, while Antedon carinata of the Indian Ocean and 

 East Pacific is a common species in the West Atlantic. 



1 Abhandl. d. k. Akad. d. Wiss. Berlin, Jahrg. 1847 [1849], p. 245. 



2 Trans. Linn. Soc. Lond. (Zool.), ser. 2, 1877 [1879], pi. i. figs. 6-10. 



