8 2 ECHINOIDEA. I. 



covered by one large plate and several small ones. The pores are trigeminate, but placed in an almost 

 straight line; only in the lower part of the areas they are distinctly seen to be trigeminate. The spines 

 are rather highly thorny, those nearest to the peristome curved. The globiferous pedicellarise without 

 any neck; the blade with simple edges, not connected by cross-beams; 2 — 3 teeth on either side. The 

 spicules irregular, three-radiate. The auriculae are formed as two narrow crests, not joining above. 



This little Echinid recalls to some degree Prionechinus A. Ag., and together with the latter 

 genus and the genera Trigonocidaris, Temnechinus, and Cottaldia it may be taken to form a special 

 group of the Temnopleurids. I shall not, however, here enter into a nearer examination of the 

 classification of the Temnopleurids, as I have not yet studied this question sufficiently, but shall only 

 make some observations with regard to the mentioned genera, which I have had occasion to examine. 

 Especially Prionechinus and Cottaldia stand in need of a more thorough description than has hitherto 

 been given, and I have in British Museum seen the type specimens of both of these genera. 



Prionechinus sagit tiger A. Ag. According to A gas si z only badly preserved specimens of this 

 species are found in the collections from < Challenger >. I have, however, seen a very well preserved 

 specimen from st. 218, and the figure (Chall. Ech. PI. VI. a. Fig. n) of the whole animal given by 

 Agassiz is, I suppose, taken just from this specimen. Further I have seen a specimen from st. 207, 

 determined as Prionechinus sagittiger; it is, no doubt, a quite different genus. The specimen from 

 st. 218, which corresponds to the habitus figure of this species given by Agassiz, must then be 

 considered as the type of it. 



«There is but a single row of plates of pores of equal size in the ambulacral zone>, it is said 

 in the description (Chall. Ech. p. 109). I do not understand the meaning of this sentence; according to 

 my observations the ambulacral areas show no unusual structures. — It is further said in the descrip- 

 tion that the pairs of large pores are arranged in a single vertical row , and according to PL VI. a. 

 Fig. 14 there are only two pairs of pores for each ambulacral plate. This does not at all hold good 

 with regard to Prionechinus; first this figure is no doubt drawn from the specimen from st 207, in 

 which the pores are really very large and form a straight line, and secondly the figure is incorrect 

 — also in this specimen 3 pairs of pores are found for each ambulacral plate. In the real Prionechinus 

 the pores are very small, and only one pore for each tube foot is seen distinctly. There are as usual 

 three pairs of pores for each ambulacral plate. — «In all the buccal plates the tentacle of one of the 

 pairs is rudimentary or even wanting?. The meaning of this indistinct sentence is that in each pair 

 of buccal tentacles one is rudimentary or wanting; it is seen on the Fig. 12 of Agassiz — and in the 

 specimen from st. 207. Perhaps this fact also applies to Prionechinus) it is now and then found in 

 Hypsiechinus , so that the feature is not at all unique. The peculiar spines resemble those of Hypsi- 

 echinus, but they are not curved. The spicules are bihamate, but very few, in most of the tube feet 

 none are found. The sucking disk is typically developed. — <The pedicellarise are numerous — ; they 

 are all of the large-headed slender-stemmed form*; Agassiz gives no more informations of the pedi- 

 cellarise, and no figures are given. The four usual kinds of pedicellaria; are found. The globiferous 

 ones (PI. VII. Fig. 29) have only one, unpaired lateral tooth on the blade, the edges of which are thick, 

 not connected by cross-beams. The poison glands are very small, not reaching to the basal part of 



