6 DR. P. H. CARPENTER ON CERTAIN POINTS 



remaining genera. It will then be convenient for descriptive 

 purposes to denote tlie five radials by the letters A-E, as I have 

 done in the case of the Crinoids * and Blastoids, taking the an- 

 terior radius as A, and those to the right and left of the anus as 

 C and D respectively t. The infrabasals, being radially situated, 

 may then be denoted by the corresponding small letters, plates c 

 and d being those which, in all the above-mentioned genera, are 

 fused into the large double plate 3 (PL I. figs. 3-8). 



Above and alternating with the radials of EcMnoencrinus are 

 the five plates of the fourth cycle (15-19), which Forbes called 

 supra-ovarian, and Volborth radial axillaries. I have endeavoured 

 to show, however, that the plates in Echinoencrinus which really 

 represent the radials of other Echinoderms are the centrolaterals 

 or second parabasals of Volborth ; and these, together with the 

 two series of plates in the dicyelic base, make up the complete 

 dorsal cup, such as we find in many Asterids, Ophiurids, and 

 Crinoids. But it is not easy to assign any definite homologies to 

 the fourth series of plates in the Cystidean calyx, even supposing 

 that they are always identical in character. In Hemicosmites 

 (fig. I.) two of them are distinctly radial, and one is interradial, 

 while the other three have no definite position. They sometimes 

 alternate very regularly with the radials, as in IJchinoencrinus 

 (PL I. figs. 3, 4), and so would almost seem to be interradials. 

 In certain genera one of them is missing, and not always the same 

 one, as I shall show immediately. But even in Ecliinoencrinus 

 there are indications of their being in relation with tlie divisions 

 of the lobate peristome, and in the somewhat irregular calyx of 

 Glyptocystis (PL I. fig. 8) each of them supports an ambulacrum, 

 a point to which I shall return. , , . 



All the three Eussian species of EcMnoencrinus % have two 

 pore-rhombs in the base of the cup, which are situated on plates 



* " On the Genus Actinometra, Miill., with a Morphological Account of a 

 new Species from the Philippine Islands," Trans. Linn. Soc, ZooL, 1879, vol. ii. 

 p. 26. 



t The lettering used above follows the course of the coiled gut of a Crinoid, 

 as seen from the ventral side, and it thus goes in the reverse direction to Forbes's 

 numbering of the Cystidean plates, as seen from the dorsal side. 



I I have not attempted to go into the complicated question of the synonymy 

 of this genus, but have simply made use of the names employed by Volborth in 

 his memoir " Ueber die Echinoencrinen " (Bull. Acad. Imp. Sci. St. Peters- 

 bourg, 1842, tome x. p. 293). 



