OF THE RERGUELEN REGION OF THE GREAT SOUTHERN OCEAN. 383 



Ophiophyllum sp. (?). 



Ophiothamnus sp. (1). 

 *Ophiotholia supplicans, Lyman. 

 *Ophiozona atellata, Lyman. 



ECHINOIDEA : 



Aceste bellidifera, 1 Wyville Thomson. 

 Aspidodiadema 2 microtuberculatum, Agassiz. 

 Brissopsis luzonica (Gray). 

 Cystechinus clypeatus, 3 Agassiz. 

 Echinus elegans (Diibeu and Koren). 



* Phormosoma asterias, Agassiz. 



# ,, hoplacantha, 4 Wyville Thomson. 

 Pourtalesia laguncula, Agassiz. 



Salenia hastigera, Agassiz. 



disk, vertically ; which shows that the muscular tension must have some peculiar proportion. . . . The peculiar 

 twisting upward of the arms and disk of Ophiomyces is explained by the absence of radial shields, a want not yet 

 observed in any other genus. It seems, then, that one Junction of radial shields is to keep the disk in shape, somewhat 

 like the action of the sticks of an umbrella. — (Lyman, Zool. Chall. Exp., part 14, pp. 240, 242.) 



1 At first glance Aceste bellidifera appears one of the most remarkable of Sea-urchins. . . . The enormous develop- 

 ment of the sucker of the odd anterior ambulacrum is an eminently embryonic feature ; it exists in the youngest stages 

 of all the Spatangoids of which we know the development. . . . The general outline of the test as seen both in profile 

 and from above is strikingly similar to that of the Schizasterid;e. In fact, this genus is of the greatest interest, showing 

 as it does striking affinities on the one side to the Schizasteridae and other Spatangina, such as Brissopsis, and on the 

 other to the Pourtalesiae, not only in the structure of its ambulacral system, but also from the position and shape of 

 the actinostome, and the more or less cylindrical test modified in its outline from its Schizasterid affinities. — (Agassiz, 

 Zool. Chall. Exp., part 9, pp. 195-6.) 



2 Aspidodiadema is a most interesting genus, intermediate between the Cidaridaa proper and the Diadematidse. 

 It has like the latter a thin test, with long hollow primary spines nearly straight, and strongly verticillate, especially 

 in the young. . . . The most remarkable feature of this genus is the structure of the ambulacral system. — (Agassiz, 

 Zool. Chall. Exp., part 9, pp. 64-5.) 



3 The test of this species [Cystechinus clypeatus] is quite stout, judging from the thickness of the fragments 

 preserved. In the specimens from the greatest depths at which this species has been found, the test is much thinner 

 than in the fragments which are found near the 1000 fathom line. As a general rule among the Pourtalesise, the test 

 of the different species having an extended bathymetrical range varies very materially in thickness, according to the 

 depth at which the specimens were dredged, specimens of the same species from shallower regions having pretty 

 generally a comparatively stouter test. — (Agassiz, Zool. Chall. Exp., part 9, pp. 149-150.) 



4 Phormosoma hoplacanthais the largest Sea-urchin with which I am acquainted. It measures no less than 312 mm. 

 in diameter, and when fully expanded, must have been a striking object. This species is remarkable for the large 

 size of the primary tubercles, arranged both on the actinal and abactinal surface of the interambulacral areas in 

 horizontal rows ; on the abactinal surface they are distant, separated by large secondaries and miliaries, irregularly 

 arranged on the coronal plates. ... In alcohol the colour of the specimens of this species is dark violet, almost 

 black both for the test and spines, and this formed a marked contrast to the white tips of the spines on the actinal 

 surface. The existence of primary spines tipped with hoofs as in the Arbaciadaj is an interesting structural feature, 

 connecting groups which thus far seemed somewhat isolated in their relationship to other Echinids. Thomson speaks 

 of the wear of the base of the cones as if they had been in use for " vigorous locomotion " over the ground, as we know 

 to be the case in one of the species of Arbacia of the eastern North American coast. In the Echinothuridse the 

 conical tip does not extend along the sides of the extremity of the spine, forming, as in the Arbaciadce, a kind of cap ; 

 it is merely attached by a nearly horizontal base to the more flattened end of the spine. In consequence of this mode 

 of attachment the tip is frequently lost.— (Agassiz, Zool. Chall. Exp., part 9, pp. 101-2.) 



VOL. XXXVIII. PART. II. (NO. 10). 3 F 



