ECHINOIDEA. I. IO i 



specimen of a diameter of 65 mm ), the edge of the mouth not bent inward. There are very few spines 

 on the abactinal side, almost only the primary ones, and as the plates 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 much in 

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

 equal size in both series. The buccal membrane with numerous, lengthy, simple fenestrated plates 

 outside the buccal plates; inside of these they are small and a little less perforated, as in E.Alexandri. 

 The colour is beautifully red, the point of the spines white. The globiferous pedicellarise (PI. XVIII. 

 Fig. 17), which are very few in number, have i i lateral tooth, but are otherwise similar to those of 

 Ech. a/finis; also the tridentate pedicellarise are scarcely to be distinguished from those of E. affinis. 

 On the other hand the ophicephalous pedicellarise are very characteristic, lengthy, and the teeth in 

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

 Fig. 37). Triphyllous pedicellarise of the common form; spicules bihamate. There can be no doubt 

 that this is a new species of Echinus, closely allied to E. elegans, 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. A g a s s i z has determined these specimens partly as Ech. 

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

 That these determinations are incorrect is a sure fact Ech. elegans* from Tristan d'Acunha is a large 

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

 (see the description below), but its tridentate pedicellariae are narrow as in Ech. affinis. <tEch. nor- 

 vcgicns-a from Japan is absolutely not this species; as far as I am able to see from my notes, it 

 must be Ech. lucidus; the pedicellarise are quite agreeing with those of that species. The speci- 

 mens from Patagonia, at all events, are not Ech. norvegicus; 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 plates; 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. magellanicus Phil. The incorrect referring of 

 these specimens to Ech. norvegictts has unfortunately given rise to the fact that this species is now 

 constantly 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 prominently*. This description of the spines is 

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

 a peculiar silky gloss; further that the primary spines round the mouth are curved in the point, and 

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

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

 ocular plates reach to the periproct, which is large and covered by numerous small plates among 

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



