66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



decentralization, leads in the most extreme cases to an obliteration of the 

 sharp limits between organ and person. 



As to the relations of the Echinodermata to other divisions of the 

 Animal Kingdom, it is certain that in some points they have distinct 

 relations to other Enterocoelia, and especially to Balanoglossus and the 

 Chordata, but as to these so little is yet certainly known that it is better 

 to refrain from any further speculation. 



OpMopteron elegans.* — Prof. H. Ludwig gives an account of a 

 remarkable new genus of Ophiurids, the type of which appears to be 

 natatory. A single example was found at Amboina by Dr. Brock. It 

 is most remarkable for having on each arm-joint a pair of large fins. 



The disc has a transverse diameter of 6 mm., and each arm is about 

 36 mm. long ; the latter with the fins are at their base 5 • 5 mm. broad, 

 and without the fins hardly 1 ■ 5 mm. The lateral Aields form a high 

 ridge or plate on either side of the arm. The arm-spines are transparent, 

 and form hooks, thorned spines, or supports for the fi.ns ; in the com- 

 position of these last two spines enter. They are articulated by a 

 thickened base, and suddenly taper to a thin rod, which gradually 

 becomes thinner ; they do not, as a rule, end in a simple tip, but fork 

 in such a way that the two branches of the fork lie close to one another. 

 The fins are formed by a thin transparent membrane, in which we may 

 distinguish an inner margin attached to the ridge of the lateral shield, 

 a free anterior edge directed towards the tip of the arm, a free outer 

 edge, and a free hinder edge directed towards the base of the arm. 

 The direction taken by the line of insertion of the fin is such that the 

 anterior edge arises on the ventral and the hinder edge on the dorsal 

 side of the arm. The successive fins lie over one another like the tiles 

 of a roof ; the anterior and posterior margins are not directly supported 

 by the rod, but by a delicate fringe of the fin-membrane which extends 

 along the spines. 



No less remarkable than the fins are the peculiar structures formed 

 by the dorsal spines of the disc. These give rise to a number of fine 

 and ordinarily six-sided funnels ; each of these consists of a short, thick 

 spine, which, at its outer edge, is continuous with six fine spines, so con- 

 nected with one another as to form a funnel, the delicate membranous 

 wall of which is supported by the six fine spines. The funnels are 

 wanting on the soft, thin, transparent ventral membrane of the disc. 

 The peristome has the general characteristics of OjoMothrix and Ophio- 

 gymna, and with the former of these the new genus seems to be most 

 closely allied. The structure of the fins may remind us of the mem- 

 brane which connects the adambulacral spines in the Pterasterid^. 



Ophiurid Fauna of Indian Archipelago. f — Herr J. Brock collected 

 sixty species of Ophiurids during a year's voyage in the Indian Archi- 

 pelago, a number of which, in addition to the OpMopteron described by 

 Prof. Ludwig, are new. The new genera are OpMoeethiops and Ophio- 

 sphsera, and a new genus Liltkenia is instituted for a species from 

 Cape York, and Ophiothela HoldswortM E. A. Smith forms the type of 

 Gymnolophus : all these are regarded as allied to OpMothrix, and the 

 distinguishing characters are pointed out. A table is given showing the 

 points of all the Ophiothrix-like genera. 



* Zeitschr. f. Wiss. Zool., xlvii. (1888) pp. 459-64 (1 pi.). 

 t T. c, pp. 465-539. 



