ECHINOIDEA. I. 123 



pedicellarice they are so very similar to albus, that herein scarcely any specific difference can be pointed 

 out. In g-ibbosus, however, I have only seen a small form of tridentate pedicellarise (PI. XVII. Fig. 12); 

 but I suppose that also the peculiar large form is found in this species, and likewise may perhaps 

 the small form be found in the two other species, although I have not found it. It is, however, to be 

 noted that gibbosits has only 4 pairs of pores, while the two others have 7 8 pairs; and so it would 

 be no strange thing, if its tridentate pedicellariae were different from those of the others. As in 

 albus only very few bihamate spicules are found. Agassiz (Rev. of Ech. p. 444) states that three 

 ocular plates reach to the periproct; on the specimen I have examined (Challenger st. 304, western 

 coast of Patagonia), no ocular plate reaches to the periproct. The same fact holds good with regard 

 to bullatus. (Of Str. bulletins I have examined the type specimens in British Museum, of albus a couple 

 of specimens are found in the museum of Copenhagen.) 



That these species are nearly related is quite undoubtful, and it is as sure a fact that they have 

 nothing to do with the real Strongylocentrotus-spzcizs. They must form a separate genus getting the 

 name of Lox echinus Desor 1 ), which has just been established for Echinus* albus Mol. As already 

 mentioned the globiferous pedicellarise are constructed as in Parcchinus (miliaris etc.), apart from the 

 short neck, and I must regard these two genera as closely allied, so that Loxechinus is chiefly to be 

 regarded as a polypore Parcchinus. That the whole habitus of the Loxec/iinus-species recalls Par- 

 echinus very much, speaks, of course, together with the other features, also in behalf of such a rela- 

 tion, although a similar habitus alone in no way can be regarded as a proof of near relationship 

 (comp. Pseiidocentrotus depressus and Anthocidaris homalostoma}. 



Strongylocentrotus limdus (Lamk.). Of this species, which is so well known especially by the 

 examinations of Valentin, I can give no new informations; I shall only here mention the features 

 which in my opinion are of essential importance for the determination of its systematic position, but 

 which are generally omitted in the systematic descriptions. A primary tubercle is found on all the 

 ambulacral plates; in the lower ambulacral plates there are only three pairs of pores. In the smaller 

 specimens all the ocular plates are shut off from the periproct, in the larger ones one or two may 

 reach to it. The buccal membrane contains rather few fenestrated plates ; most of those outside of the 

 buccal plates are thick, round, and carry pedicellarise; nearest to the edge a sphseridia may be found, 

 sometimes one more may be found farther in on the buccal membrane. There are no spines on the 

 buccal plates or on the other plates of the buccal membrane. To be sure Valentin says (Anatomic 

 dn genre Echinus, p. 62): il existe encore a la surface de la membrane buccale de petits piquants 

 microscopiques , dont la structure ne differe en rien de celle des piquants*; but I suppose it to be 

 stalks of pedicellarise he has mistaken for spines. On the figure to which he refers, no spines are 

 found, but only stalks of pedicellarise. The globiferous pedicellarise are most nearly alike to those of 

 Parechinus. The blade is quite open with i i lateral tooth (PL XVII. Fig. 19), but the edge is thick, 

 not thin and sharp as in Parcchinus. There is no neck; the stalk consists of long, thin threads, only 

 little connected, except at the ends of the stalk. (Also in the other pedicellarise the stalk is con- 

 structed in this manner.) The tridentate pedicellarise are very peculiar with long, narrow blade, 

 coarsely serrate through the whole edge (PL XVII. Fig. 21); there are no small teeth. The ophice- 



') Synopsis des Ech. fossiles. p. 136. 



16* 



