100 ECHINOIDEA. I. 



E. elrgans ■■; according to what has been stated above it cannot be closely allied to both these species, 

 and no inference can be drawn from the quite insufficient description that is not even accompanied 

 by figures. From U. S. National Museum I have received a specimen on loan, determined as Ech. 

 Wallisi. It is a large, fine specimen of Ech. elegans (only with somewhat shorter spines and higher 

 than the typical form); but it is unfortunately not certain that it is really identical with Ech. Wallisi, 

 as it does not agree very well with the description, except in the colour. Thus Ech. Wallisi must for 

 the present remain somewhat problematic. 



Most nearly related to Echinus elegans are the species: gracilis, Alexandria and lucidus, and 

 the new species described here: Ech. a f finis n. sp. and a flan fie us n. sp. ; they have all of them a 

 primary tubercle on every ambulacral plate; numerous fenestrated plates imbedded in the buccal mem- 

 brane (this feature, however, not observed in E. lucidus); no ocular plates reach to the periproct; the 

 spicules bihamate; all with rather strong, long, and pointed spines. Ech. Alexandri is rather sharply 

 distinguished from the other species by its tridentate pedicellarite, which are especially broad and 

 comparativelv short (PI. XX. Fig. i), while in the other species they are long and narrow (PI. XVIII. 

 Fig. 4). In the smaller forms of tridentate pedicellarise the blade is more flat and broad, and the upper 

 end of the apophysis is a little widened as a more or less perforated plate; in the larger forms there 

 is some mesh-work in the bottom of the blade. As in E. elegans there are in these species all transi- 

 tions between the largest and smallest tridentate pedieellarise; to be sure, I have only seen a few of 

 smaller size in Ech. lucidus, but as these resemble to a high degree, those of a corresponding size in 

 the other species it may be supposed that also in this species large tridentate pedicellariaa will be 

 found of the same form as in the other mentioned species. In all these species the tridentate pedicel- 

 larise are upon the whole so similar, that reliable specific characters can scarcely be found in them 

 (PI. XVIII. Figs. 15, 21—22, 26 — 28). -- The globiferous pedicellaria; in Ech. Alexandri have generally 

 3 — 4 teeth on either side, in the other species there are most frequently 1 — 1 or 1—2 lateral teeth. 

 Also the globiferous pedicellariae are very similar in all these species (PI. XVIII. Figs. 9— n, 16—18, 

 PI. XIX. Fig. 18). 



Ech. affinis is distinguished from the other species by the peculiar feature that the two series 

 of tubercles in each ambulacral area are of unequal size or quite irregular; there is, however, always 

 a primary tubercle on every ambulacral plate (see the particular description below). Ech. gracilis is 

 easily distinguished from the other related species by its beautiful green coloration; the tridentate 

 pedicellariae (PI. XVIII. Figs. 15, 21) are a little more serrate below than in the other species, it is 

 however, scarcely a reliable character. Agassiz, in his description of it (Rev. of Ech. p. 293), says: «this 

 species holds an intermediate position between E. Flemingii Ball and E. mclo Lamk., to both of which 

 it is allied». This, according to what is stated here, is incorrect; its nearest relations are E. elegans 

 and the other species named here. — Ech. lucidus, of which species Prof. Doderlein has kindly lent 

 me a specimen for examination, is most similar to Ech. Alexandri, but may easily be distinguished 

 from this species by its tridentate and globiferous pedieellarice (PI. XIX. Fig. 18). 



In Challenger-Echinoidea (p. 114) Agassiz mentions Echinus acutus from st. 343, off Ascension, 

 425 fathoms. I have had occasion to examine these specimens in British Museum, and I must 

 positively assert that it is not Ech. acutus. The test is high; the peristome very small (i5' nm in a 



