REPORT ON THE CRINOIDEA. 309 



externally between the angles of the radials, as seen in PI. V. fig. 5b. The radials 

 somewhat resemble those of Actinometra maculata, in not completely covering the 

 centro-dorsal (PI. V. figs, la, 5a) ; but the ventral pair of muscle-fossee on their 

 articular faces is even more reduced than in that type (PI. V. figs, lb, 5b, 5c). The two 

 species are closely allied, however, and may eventually prove to be connected by inter- 

 mediate forms. Actinometra stelligera is the larger of the two, and has a greater 

 number of arms, palmars being always developed, and sometimes post-palmars also ; 

 while there are no post-distichal axillaries in the two examples of Actinometra maculata, 

 which also has rather more spinous cirri. The two species further present the same sort 

 of difference in the carination of the basal pinnules as occurs between Actinometra 

 Solaris and Actinometra pectinata. In Actinometra maculata there may be keels on 

 the pinnules of the second to ninth brachials, whereas in Actinometra stelligera there 

 is no sign of carination on the basal joints of the first pinnule, though there may be 

 on that of the fifth on the same side (10th br.). 



Reversions to the more normal type of arm-structure sometimes occur. Thus, for 

 example, the outer arm of the right hand ray in the figured specimen of Actinometra 

 stelligera (PI. LVIII. fig. 1) has the first two brachials articulated like the radials and 

 distichals ; whereas in the other arm borne on the same distichal axillary, and in three 

 similar arms of the centre ray, these two joints are united by syzygy. Two curious 

 abnormalities of the disk have also come under my notice. In one case there are two 

 mouths and two anal tubes, as shown in Part I. pi. lvi. fig. 8 ; while in the other the 

 anal tube is close up to the peristome, a little to one side of the median line, and not 

 central as is usually the case. 



The depth at which this species was dredged is not known with certainty ; but it 

 was probably either 210 or 255 fathoms, the third depth at this locality being an 

 improbable one for an Actinometra, especially as the type belongs to the littoral fauna 

 at Fiji, Samoa, and Tonga. There is a closely allied, if not identical, species from Zebu 

 in the Museums at Dresden and Vienna. Semper's Philippine collection also contains a 

 fine species belonging to this group, which differs from Actinometra stelligera in the 

 presence of a third axillary beyond the distichals, and in the relatively smaller size of 

 the centro-dorsal, so that not only the second radials, but also portions of the first, are 

 visible externally. It is the type to which I have occasionally referred as Actinometra 

 nigra, Semper, MS., and is remarkable for the great development of the branches of the 

 axial cords of the arms and of the par-ambulacral network which is connected with them 

 in the ventral perisome, and also for the large size of the radial blood-spaces beneath 

 the ambulacra, the existence of which in Antedon rosacea has recently been denied by 

 Messrs. Vogt and Yung. 1 Figures illustrating these points were given in Part I. pp. 121, 

 122, and pi. lxi. fig. 6. 



1 Traite d'Anatomie compare pratique, 1886, Livr. vii. p. 538. 



