ECHINOIDEA. I. IO5 



giving any information whatever of them; as far as I can see they are nomina nuda, and Philippi 

 deserves no praise for having introduced them. 



Echinus nmUicolor Yoshiwara I have not seen; the description gives no information of pedi- 

 cellariæ, spicules, and several other important featnres, so that nothing can be said with regard to its 

 being a genuine Echinus or not. 



The species Ech. viiliaris, microtiiberculatus, angulosus, vrrruailahis, Robillardi, and darnlcycnsis 

 are no genuine j5'f/;/«?«-species. For the present then they may be left out of consideration, while the 

 question of the grouping of the species above nientioned is treated. 



Do all these species really belong to the same genus, or can there be any question of grouping 

 them into more genera? The question is partly answered already, Koehler having established the 

 genus Ster echinus on E. margaritaceus (without knowing, to be sure, that it was this species). The 

 characters upon which the genus is based, are: the comparatively large central plate, the narrow apical 

 piates, of which all the ocular piates reach to the periproct, and the comparatively great height of 

 the coronal piates. — The character of the apical piates is evidently useless, all the ocular piates being 

 shut off from the periproct in smaller specimeus. Also the central plate seems to me to be an only 

 little valuable character; in e\-ery }Oung Echinus the central plate is distinct, it does not disappear till 

 a later stage, other small piates being formed round it, so that at last it cannot be distinguished from 

 the secondary piates. Neither seems the height of the coronal piates to be a valuable character, as it 

 varies much according to the size of the animal. — Now it is not in>- meaning to say that the genus 

 Sterechinus cannot be kept up, only that the characters upon which it is based, cannot be used; we 

 must seek other characters for it. May, then, other characters be found by which to group 

 the species? 



Amoug the characters mentioned above one is found that might beforehand be thought to be 

 of great importance, viz. whether a primary tubercle is found on every or only on every other ambu- 

 lacral plate. In the species csculcntus^ aciihis, melo, margaritaceus, and Neuniayeri a primar\- tubercle 

 is only found on every other ambulacral plate, in all the other species it is found on every ambulacral 

 plate. That this feature, however, can be of no primary importance is evident from the faet that it 

 separates Ecli. margaritaceus and horridus, two species that are, no doubt, very closely allied. — An- 

 other character of undoubtful valne is whether the buccal membrane contains numerous fenestrated 

 piates, or is quite (or almost) naked, at all events outside of the buccal piates. Numerous piates in 

 the buccal membrane are found in the species: csculcntus, acutus, iiicio, elegans, gracilis, Alexandri, 

 affinis, atlaiiticus, and lucidits (not examined); naked buccal membrane is found in the species: marga- 

 ritaceus, horridns (not examined), N'eumayeri, magcl/anicus, and albocinctus. This character does not 

 separate allied species, but divides them into two groups which seem to be well divided as to habitus, 

 but where the species of each group seem to be mutually ratlier closely allied. It is evident then 

 that we have here a specially important s^stematic character. Another feature gives quite the same 

 grouping of the species, viz. whether the edge of the tridentate pedicellariæ is thick and provided with 

 numerous small teeth arranged in more or less regular transverse series, or it is thin and simply ser- 

 rate. In the former group, Ech. esculentits etc, the edge is thick with transverse series of small teeth, 

 in the latter group, Ech. margaritaceus etc, it is simply serrate. This character, however, is not quite 



The Ingoir-Expedition. IV. i. 14 



