lOO ECHINOIDEA. I, 



E. elcgans»\ according to wliat has beeu stated above it caiinot 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 Eck. 

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

 than the typical form); but it is unfortunately not certain that it is realh' 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 nearh- related to Echiiius clegaiis are the species: gracilis, Alcxaiidri, and lucidus, and 

 the new species described here: EcJi. affinis n. sp. and aflaiiticns n. sp. ; tlie\- have all of theni a 

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

 brane (this feature, however, not observed in E. Incidus); no ocular piates reacli to the periproct; the 

 spicules bihamate; all with rather strong, long, and pointed spines. Eck. Alcxaiidri is rather sharph' 

 distinguished from the other species by its tridentate pedicellariæ, which are especiall}- broad and 

 comparatively 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 pedicellariæ the blade is more flat and broad, and the upper 

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

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

 tions between the largest and .smallest tridentate pedicellariæ; to be sure, I have only .seeu a few of 

 smaller size in Ech. litcidiis, 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 pedicellariæ will be 

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

 lariæ are upon the whole so similar, that reliable specific characters can scarcel}- be found in them 

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

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

 Also the globiferous pedicellariæ are very similar in all these species (PI. XVIII. Figs. 9— 11, 16—18, 

 PL XIX. Fig. 18). 



Ech. affinis is distinguished from the other species b}- 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 

 pedicellariæ (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. Flcmiiigii Ball and E. mclo Lamk., to both of wliich 

 it is alliedi. This, according to what is stated here, is incorrect; its nearest relations are E. clegans 

 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 ma)- easily be distinguished 

 from this species by its tridentate and globiferous pedicellariæ (PL XIX. Fig. 18). 



In Challenger-Echinoidea (p. 114) Agassiz mentions Echii/Jts acalits 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 (15™™ in a 



