ECHINOIDEA. II. 



since one is known only from the Northern Atlantic, the other only from the Malay Archipelago and 

 Japan, it may be well to keep the Pacific form as a Var. gibbosus, for the present, though it seems 

 to be distinguished almost alone by the character of its geographical distribution. 



The other species from the Challenger, Hemiaster zonatus, is so very imperfectly described 

 that it is impossible to found upon that description any definite opinion of its claim to form a separate 

 species. The figures, to be sure, show it clad in a close and uniform coat of spines; but also in 

 H.expcrgitus the coat of spines may be rather close -- and in the description of //. Mentzi (Blake- 

 Echini. p. 66) the tuberculation of //. sonatus is stated to be more distant, as it is in // expergitus. 

 It is thus, evidently, no very reliable character. The large fascicle and the deep anal groove do not 

 seem very reliable characters either, as it may be almost exactly similar in expergitus, so that it does 

 not seem very improbable, when Agassiz thinks the differences from cxpcrgitus may be due only to 

 age. On examining the type-specimens in the British Museum, I get the following result. The specimen 

 from St. 8, off Gomera, Canaries, is undoubtedly //. expergitus, with which species it also agrees 

 exactly in the pedicellariae; but the specimen from St. 126 (off Rio Janeiro, 750 fms.) is undoubtedly 

 something quite different. Unfortunately the specimen is completely crushed, only the apical and the 

 actinal regions being tolerably preserved. As regards the structure of the test, it may be pointed out that 

 the labrum does not reach the second adjoining ambulacral plates. There are only two genital openings 

 and the apical system is not ethmophract as in Hemiaster ; the madreporic plate extends backwards 

 and separates the posterior ocular plates, but is not prolonged into the posterior interambulacrmn. 

 The peripetalous fascicle is more SchizasterAfas, not round as in the figured specimen, and it is not 

 so broad as in that figure; any trace of a latero-anal fascicle cannot be seen but that is no definite 

 proof of its non-existence, on account of the poor condition of the specimen. For the rest the specimen 

 is abnormal, the right anterior petal lacking; the left side is normal, showing the posterior petal only 

 one third the length of the anterior petal. The spines are simply widened towards the point, not of 

 the elegant shape of those of Hemiaster. The globiferous pedicellarise are very different from those of 

 H. expergitus; the valves (PI. XV. Figs. 3, 7) enclose a large (probably glandular) space, which opens 

 with a small pore at the base of the single, compressed tooth, which terminates the long and slender, 

 curved blade a structure exactly similar to that found in Schizastcr fragilis a. o. (comp. below, p. no). 

 The tridentate pedicellariae are like those of expergitus, but only the small form was found; the 

 rostrate pedicellariae (PI. XV. Fig. 11) differ somewhat from those of expergitus, as seen by a comparison 

 of the figures. That the spicules of the tube-feet are few in numbers can scarcely mean anything as 

 a distinguishing character, since there is considerable variation in this respect in expergitus. 



Quite recently Professor Doderlein (Echinoidea d. deutsch. Tiefsee-Exp. p. 247) has referred 

 with some doubt a specimen from the Rockall-Bank to Hemiaster zonatus, and probably he is quite 

 right herein, judging from his figures and description of the pedicellariae. The globiferous pedicellariae 

 are seen to agree with those figured here from the type specimen ; the single difference, a swelling on 

 the stalk, which I have not found in the type specimen, can scarcely be of any importance. More 

 different are the rostrate pedicellariae but as in expergitus these pedicellariae differ rather much in 

 form, the difference herein can scarcely necessitate a separation. Unfortunately also Professor Doder- 

 lein's specimen was quite crushed, so that we must still remain ignorant of the structure and form 



