JQ2 ECHINOIDEA. II. 



area. The bathvmetrical distribution i.s from 220 (or 170, conip. below, //. Mciifzi) to 1700 fatlioins 

 («Talisman»). 



Besides the species H.expcrgilns four more recent S2:)ecies of tlie genus Hcviiastcr (exc\.A/)<i//ts) 

 have been described, viz. Hemiastcr gibhosus A. Ag., zoiuihis A. Ag. both from the «Challenger >, 

 //. Mcntzi A. Ag., from the « Blake , and //. florigerus Studer, from the «Gazelle;>. (The Iloniastcr 

 apicatus Woods is referred by Woods himself to the subgenus Rhiiiobrissus and therefore, being no 

 true H&iniasicr, 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 //. cxpergitiis. 



In his description of Hemiastcr gibbosus («Chall.»-Ech. p. 184, PL XX. 5—16, 22) Agassiz does 

 not point out by which features this species is distinguished from H. expergitus, and a careful analysis 

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

 («Siboga»-Ech. p. 182) has had some specimens of H. gibbosiis, but he only remarks that he finds them 

 answering well to the description given by A gas si z. Through the kindness of Professor M. Weber 

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

 with equal-sized specimens of //. expergitus. and finally I have examined the , Challengers-specimens 

 in the British Museum. The comparison of //. gibbosus and expergitus gives the following results. 



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

 shown in Fig. 6. PI. XX of the t Challengers-Echini, all the specimens being wider in front than behind, 

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



of the specimen figured in PI. XX. 5 ' is almost quite as in cxpergitiis. 

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

 any distinguishing character. Agassiz points out tliat the jjlates of 

 the lateral posterior interambulacra are comparatively bare — but in 

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

 difference herein between the specimen of gibbosus before me and 

 o%y'\°-°°°^°^if'°sit\\°'}l'l-'''\V''l' eciual-sizcd cxpergitzis. — *:The biviuni is separated from the trivium b\- 

 • •-"S-V5%°;».:;;''.°<j<,Vo"«.''.";-v»*«°*"' two large intercalated interambulacral plates:. I suppose, that by these 



Fig. 19. Abactinal part of the left ^^^ ^j^^jj^ ^j^^ ^^^,^ l^ j^^^^ ^^^j^j^j^^ ^j^^ fasciole between the anterior 



])Osterior Iiitcranibulacriiin 141, of o i 



iiemiasiei' gibbosus; comp. with and posterior petal seen in the Fig. 9. PL XX. The figure, however, must 

 PI. XX. Fig. 9 of the «Challenger»- ^ • , , t 1,1 • • , , • .- , ■ 



Echiiioidea certauily be wrong. It would be a quite exceptional thing to find 111 



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

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

 quite as in expergitus of the .same size. U could not be made out with certaiiit\-, how this is in the 

 - Challenger ^>-specimen.s, but I do not doubt in the slightest that they will show the usual structure. 

 (In the largest specimen of expergitus the fasciole traverses the 5tli- 7th ].lale in tliese interambu- 

 lacra). The «intermiliary granulation , which Profes.sor Agassiz figures (PL XX. Vvg. 13), I am unal)le 

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

 men of expergitus it is well developed, though not so close as in tlie figure quoted. 



■ In the explanation of Plates (p. 292I it is stated that Fig. 5 and 6 represent the same specimen which is evidently 

 impossible and in contradiction to tlie text (j). 184). 



