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



6. Actinometra rubiginosa, Pourt., sp. This form was originally described as an 

 Antedon by Pourtales, before the two genera were distinctly separated. 1 



7. Actinometra coppingeri, Bell. The formula assigned to this type by Bell 2 is 

 that of a ten-armed species, with a syzygy in the third brachial. But the number of 

 arms varies from twelve to twenty, and there is a syzygy in the second joint above the 

 distichal axillary. 



8. Actinometra parvicirra, Mull., sp. This protean type has been variously 

 described under the following names — annulata, mertensi, rneyeri, polymorpha, 

 timorensis, wahlhcrgi. 



9. Actinometra variabilis, Bell. This species appeared in my former list 8 in the 

 group (A. 3.3.), this being the formula which I was led to assign to it on the basis of that 

 previously given by Bell.' 



10. Actinometra briareus, Bell, sp. Bell has described this species 5 as an Antedon 

 with the formula A.3.2.(2) ; though the majority of the palmar series are three-jointed 

 and some of them are followed by another series of the same character. 



11. Actinometra nobilis, n. sp. Actinometra dissimilis of Part I. 6 appears to be a 

 varietal form of this t)>p>e. 



Some curious points of contrast may be noticed in the two lists given above. There 

 are three very distinct types of Actinometra in which the two outer radials are united 

 by syzygy. (l) The ten-armed (Actinometra Solaris) ; (2) those with two distichals 

 (Actinometra paucicirra) ; and (3) those with three (Actinometra typica). In the 

 latter case each subsequent division (if present) consists of only two joints united by 

 syzygy. On the other hand, all the recent species of Antedon yet described which have 

 the radials a syzygy have three distichals, while the palmars and subsequent divisions 

 either resemble the distichals, or consist of two articulated joints. Species of Antedon 

 like Actinometra paucicirra and Actinometra typica are, like those of the Solaris-ty\>Q, 

 yet to be described. 



More than half the species of Antedon belong to the simple ten-armed type with 

 articulated radials like Antedon eschrichti (PI. XXIV. fig. 11) ; while half the remainder 

 have only two joints in each of the first three arm-divisions, as in Actinometra conjungens 

 (PI. XLV. fig. l). But there are not ten described ten-armed species of Actinometra 

 which have articulated radials, nor ten with two-jointed distichal series. Both these 

 types, which together include over three-quarters of the species of Antedon, thus 

 present themselves but rarely in Actinometra. 



On the other hand, we find in this genus a much greater number and variety of the 



1 List of the Crinoids obtained on the Coasts of Florida and Cuba by the United States Coast Survey Gulf Stream 

 Expeditions in 1867, 1868, 1869, Bull. Mus. Comp. Zool, 1869, vol. i. No. 11, p. 356. 



2 Proc. Zool. Soc. Lond., 1882, p. 535. 3 Ibid., p. 747. 



♦ Ibid., p. 535. 6 u A i ert » Report, pp . 155, 163. 



6 Zool. Chall. Exp., part xxxii. pp. 110, 111. 



