ECHINOIDEA. I. lOI 



specimeii of a diameter of 65""™), the edge of the mouth not bent inward. There are very few spiues 

 on the abactinal side, almost only the primary ones, and as the piates are very high, the primary 

 spines are also widely separated; on the actinal side there are more secondary spines, they are not, 

 however, very close-set. The primary spines are of a middle length, and do not decrease mnch in 

 length towards the apical area. A primary spine is fonnd on each ambulacral plate, and they are of 

 equal size in both series. The bnccal membrane with numerons, lengthy, simple fenestrated piates 

 outside the bnccal piates; inside of these they are small and a little less perforated, as in E. Alcxaiidri. 

 The colour is beantifnlly red, the point of the spines white. The globiferous pedicellariæ (PI. XVIII. 

 Fig. 17), which are very few in nnmber, have i — i lateral tooth, bnt are otherwise similar to those of 

 Ech. affinis\ also the tridentate pedicellariæ are scarcely to be distingnished from those of E. affinis. 

 On the other hånd the ophicephalous pedicellariæ are very characteristic , lengthy, and the teeth in 

 the edge are uncommonly fine, only to be seen under especially high magnifying powers (PL XIX. 

 Fig. 37). Triphyllous pedicellariæ of the common form; spiciiles bihamate. — There can be no doubt 

 that this is a new species of Echinus^ closely allied to E. clcgaiis^ gracilis etc. ; I propose to call it Echinus 

 atlanticus. 



Presumably there are among the Echinids obtained by the Challenger»-Expedition still one 

 or two species allied to those mentioned here. Agassizhas determined these specimens partly &s Ech. 

 elegans (from Tristan d'Acnnha), partly as Ech. iwrvcgicus (from Patagonia, st. 308, and Japan, st. 232). 

 That these determinations are incorrect is a sure faet. iEcli. clcgansh from Tristan d'Acnnha is a large 

 form, very similar to Ech. Alcxaiidri., that is to say, to the most long-spined specimens of this species 

 (see the description below), bnt its tridentate pedicellariæ are narrow as in Ec/i. affiiiis. Ech. nor- 

 vegicuS' from Japan is absolutel\- not this species; as far as I am able to see from my notes, it 

 must be E.cli. lucidits; the pedicellariæ are quite agreeing with those of that species. The speci- 

 mens from Patagonia, at all events, are not Ech. uorvcgiciis; they belong to two different species, of 

 which one (3 large specimens) belongs to this group of species with a primary tubercle on all the 

 ambulacral piates; perhaps it is Ech. affinis, but I am not able to determine it with certainty after my 

 notes. The other species (4 small specimens) is Ech. viagcllaiiicHs Phil. — The incorrect referring of 

 these specimens to Ech. norvcgicits has nnfortunately given rise to the faet that this species is now 

 coustantly named among the bipolar animals. 



Ech. margaritaceus Lamk. Of this species it is justly said in «Rev. of Ech.' (p. 493) that it has 

 «very marked features*, but in the description only one of its peculiarities is mentioned, viz. the nature 

 of its covering with spines; the plate is densely covered with minute secondary tubercles carrying 

 short, slender, yellowish spines closely crowded together, which are a lower groundwork from which 

 the primary spines, long, slender, and white, project prominentl\- . This description of the spines is 

 excellent, it is onh- to be added that these spinules are richly set with fine thorns, which gives them 

 a peculiar silkv gloss; further that the priniar_\- spines round the mouth are curved in the point, and 

 that generally, but not always, some small, club-shaped spines are found on the bnccal piates. Only 

 every other ambulacral plate carries a primary tubercle. The apical area is very peculiar, all the 

 ocular piates reach to the periproct, which is large and covered by numerons small piates among 

 which the central plate is especially distinct. In small specimens all the ocular piates are shut off 



