ECHINOIDEA. I. 



I05 



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 //i it If /color Yoshiwara I have not seen; the description gives no information of pedi- 

 cellaria?, spicules, and several other important features, so that nothing can be said with regard to its 

 being a genuine Echinus or not. 



The species Ech. miliaris, microtuberculatus, angulosus, verruculatus, Robillardi, and darnleyensis 

 are no genuine Echinus-species. For the present then they may be left out of consideration, while the 

 question of the grouping of the species above mentioned 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 Sterechinus 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 

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

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

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

 little valuable character; in every young Echinus the central plate is distinct, it does not disappear till 

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

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

 varies much according to the size of the animal. — Now it is not my 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? 



Among 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 esculentus, acutus, melo, margaritaceus, and Neumayeri a primary 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 fact that it 

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

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

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

 the buccal membrane are found in the species: esculentus, acutus, ///do, elegaus, gracilis, Alexandn, 

 affinis, atlanticus, and lucid/is (not examined); naked buccal membrane is found in the species: marga- 

 ritaceus, horridus (not examined), Neumayeri, magellanicus, 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 rather closely allied. It is evident then 

 that we have here a specially important systematic character. Another feature gives quite the same 

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

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

 rate. In the former group, Ech. esculentus 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 Ingolf-Expedition. IV. i. *4 



