I02 



ECHINOIDEA. II. 



area. The bathyinetrical distribution is from 220 (or 170, conip. below, //. Alcntzi) to 1700 fathonis 

 (vTalisiiian>). 



Besides the species H.cxpergitus fonr more recent species of the genus Hctniastcr (excl. .i/v?///,v) 

 have Ijeen described, viz. Haniastcr gibbosiis A. Ag., zonatus A. Ag. both from the «Challenger», 

 //. Mnitzi A. Ag., from the < Blake , and //. florigcriis Studer, from the * Gazelle . (The Ilniiiaslcr 

 apicatits Woods is referred by Woods himself to the subgenus Rliinobr issus and tlierefore, being no 

 true Hctniastcr, does not concern us here). As for the first and third of these species it seems rather 

 probable that they will prove to be synonyms only of //. cxpcrgitns. 



In his description of FTcmiastcr gibbosus (sChall. -Ech. p. 184, PI. XX. 5 — 16, 22) Agassiz does 

 not point out by wliicli features this species is distinguished from //. cxpcrgitns, and a carefnl analysis 

 of his description and figures does not reveal any good distinguishing characters eitlier. De Meijere 

 (<-vSiboga -Ech. p. 182) has had some .sjjecimens of H. gibbosus, bnt he only remarks that he finds them 

 answcring well to the description given by Agassiz. Through the kindness of Professor M. Weber 

 I have received one of these specimen.s, 20""" in length; I have thus been able to compare the species 

 with eqnal-sized specimens of //. cxpcrgitns. and finally I have examined the cChallenger /-specimens 

 in the P.ritish Museum. The comparison of //. gibbosus and cxpcrgitns gives the foUowing results. 



The shape of the test is the same; to be snre I have seen no specimen of cxpcrgitus of the form 

 shown in Fig. 6. PI. XX of the «Challenger»-Echini, all the specimens being wider in front than behind, 

 or (the .small ones) almost elliptic. But Agassiz him.self states that the outline is variable, and the outline 



of the specimen figured in PL XX. 5 ' is almost quite as in cxpcrgitns. 

 (Comp. PI. II. Fig. i). Evidently the form of the test thus does not give 

 any distinguishing character. Agassiz points out that the piates of 

 the lateral posterior interambulacra are comparatively bare — but in 

 cxpcrgitus they may be quite as bare, and I am unable to find any 

 difference herein between the specimen of gibbosus before me and 

 cqual-sized cxpcrgitus. — «The bivium is separated from the trivimn by 

 two large intercalated interambulacral piates >. I supi^ose, that by these 

 are meant the two large piates within the fasciole between the anterior 

 and posterior petal seen in the Fig. 9. PL XX. The figure, however, must 

 certainly be wrong. It would be a quite exceptional thing to find in 

 this place two large, paired piates; I find these interambulacra in the 

 specimen before me of the usual struclure (Fig. 19), the fasciole passes over the third and fourth plate, 

 qnite as in cxpcrgitus of the same size. It could not be made out with certainty, how this is in the 

 «Challenger »-specimens, but I do not doubt in the slightest that they will show the usual structure. 

 (In the largest specimen of cxpcrgitus the fasciole traverses the 5th— 7th plate in these interambu- 

 lacra). The «intermiliary granulation , which Professor Agassiz figures (PL XX. Fig. 13), I am unable 

 to find either in the specimen of gibbosus or in cxpcrgitns of corresponding size. In the largest speci- 

 men of cxpcrgitus it is well developed, thongh not so close as in the figure quoted. 



Fig. ig. Abaclinal part of the left 

 posterior Interambiilacruin (4), of 

 Hemiastei' gibbosus; comp. with 

 PI. XX. Fig. 9 of the < Challeuger»- 

 Echinoidca. 



■ lu tlie exphiiiation of Piates (p. 292) it i.s statcd tliat Fig. 5 and 6 represent the same specimen which is evidently 

 inipo.ssiblc and in contradictiou to the text (p. 1S4). 



