ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 997 



shore to 700 fathoms, or deeper. The deep-sea genera appear to be 

 Pselopaiides, Pseudostichopus, Acanthoirochus, and perhaps Ankyro- 

 derma ; the Synaptidaa are littoral forms, and the Molpadidee are 

 making, or have made, their way to great depths. 



Six-rayed Holothurians.* — Prof. H. Ludwig found among about 

 150 specimens of Cucumaria planci at Naples five sex-radiate examples ; 

 the sixth radius and interradius" 1 were observed to be interpolated 

 between the two rays of the biviuin, and were more often to the left 

 than the right of the interradius. 



Circulatory System of Ophiurids.f — M. E. Kohler finds that 

 the circulatory apparatus of Ophiurids is very comparable to that 

 which he and Prouho have described as obtaining in Echinids. 

 There is the same structure of the madreporic gland, the same rela- 

 tions between it and the exterior on the one hand, and the peribuccal 

 ring on the other; two peribuccal rings give off branches to the ambu- 

 lacral zones, and there is no aboral circle. In Ophiurids, however, 

 the two rings do not communicate by the Polian vesicles, as they do 

 in regular though not in spatangoid Echinoidea. The Ophiurids 

 want the intestinal vessels which are so well developed in Echinoids. 



With regard to the structure of the intestine, there is, as in all 

 Echinoderms, a well-developed internal epithelium, a layer of con- 

 nective and one of muscular tissue, covered by the general peritoneal 

 envelope. The fourth layer described by Apostolides — that of external 

 cells — is really the region of nuclei, while his muscular fibres are, 

 in effect, the elongated cell-membranes. 



Revision of the Palaeocrinoidea.J — Messrs. C. Wachsmuth and 

 F. Springer define the sub-order Articulata as consisting of their 

 family Ichthyocrinidae, together with Crotalocrinus and Enallocrinus ; 

 they divide the group into the two families of Ichthyocrinidaa and 

 Crotalocrinidae, the latter being distinguished by the, possession of a 

 ventral tube or anal appendage, placed ventrally near the periphery ; 

 the higher radials are also less perfectly developed than in the other 

 family. 



The sub-order Inadunata consists of two branches, the first of 

 which is called that of the Larviformia; here we have the Haplo- 

 crinidse, which are the simplest brachiate Crinoids, and represent 

 the larva not only of the Inadunata, but of the Palaeocrinoidea 

 generally ; the Symbathocrinidae, which are very closely allied to 

 them; and the Cupressocrinidse and Gasterocrinidas, which are 

 dicyclic Crinoids. In some particulars of their arm-structure the 

 Larviformia agree with the Blastoids, and they probably possessed 

 hydrospires ; the arms are simple throughout, though exceptionally 

 some of the radials support two arms. The second branch is that of 

 the Fistulata, which is equivalent to the group CyathocrinidaB, as 

 already defined by the authors; it is now divided into families. 



* Zool. Anzeig., ix. (188G) pp. 472-7. 



f Comptes Rendus, ciii. (1886) pp. 501—1. 



J Proc. Acad. Nat. Sci. Philad., 1886, pp. 64-226. 



