ECHINOIDEA. I. 107 



Primary tubercle on e\-ery ambulacral plate; the globiferous pedicellariæ with 



2 — 4 teeth on either side, the edges not connected Sf. horrid%is. 



3. Primary tubercle on every other ambulacral plate • St. Neumayeri. 



— — - — ambulacral plate St. magcllaniciis. 



Echinus miliaris^ viicrofubcrcitlafus, and aiigiilosus form a separate group chiefly characterized 

 by the globiferous pedicellariæ (PI. XVII. Figs. i, 7). The blade is rather flat, comparatively broad, and 

 passes evenly into the basal part; no cross-beams connect the edges across the inside of the blade; 

 the edges are not thickened, and project into more or fewer teeth on either side. There is no neck; 

 the stalk as usually constructed of long threads connected by cross-beams. A somewhat similar form 

 of globiferous pedicellariæ is found in Stercchimis horridiis (PI. XIX. Fig. 22), and sometimes also in 

 Echinus Alexandri (PI. XVIII. Fig. 9]. A comparison of the figures will show, however, that they are 

 very different, even if it is not easy to point out a particular distinguishing character; the most signi- 

 ficant one is, I think, that here the edge is somewhat thickened, so that the teeth are placed on it, 

 while in EcJi. iiiilian's etc. the edge is quite sharp, and the <. teeth • are simply indentations in the 

 edge; also the whole form is somewhat different, as shown by the figures. 



The foUowing characters of the separate species must be pointed out. In Ech. miliaris the 

 buccal membrane is covered by large, thick fenestrated piates. The globiferous pedicellariæ have 

 numerous lateral teeth; the tridentate ones have a rather strong net of meshes in the bottom of the 

 blade (only the large ones); the edge is coarsely indented below, in the outer part where the valves 

 join coarsely sinuate, but the sinuations are again finely serrate; the small teeth form no transverse 

 series (PI. XVII. Fig. 11). The ophicephalous and triphyllous pedicellariæ with no conspicuous peculiar- 

 ities. — All three species have a primary spine on every ambulacral plate; in miliaris and ftiicroiuber- 

 culatns the ocular piates are shut off from the periproct, in E. aiigulosits the two (three) reach to the 

 periproct; no distinct central plate. 



Ech. »licrotiibcrculatiis agrees exactly with i/iiliaris in the structure of the pedicellariæ; it is 

 only to be observed that the tridentate pedicellariæ have rather distinct transverse series of teeth on 

 the edge. The piates of the buccal membrane are especially characteristic (PI. XVI. Fig. 14). They 

 are large, thick, greenish, and of quite another structure than in miliaris., not consisting of the usual 

 reticulation , but of a homogeneous mass of lime, in which the pores appear as deep, funnel-shaped 

 holes. Also the piates inside of the buccal piates are constructed in this way. Otherwise it is distiu- 

 guished from miliaris by its somewhat finer spines and corresponding smaller tubercles (PI. XV. 

 Figs. 8, 9) ; the colour of the test and spines is more intensely green. — In the original diagnosis of 

 Ech. microtiiberculafus'^) it is said: ambulacres å denticules trés-arquées et composées de six jjaires de 

 pores ; in Blainville's «.Manuel d'Actinologie > 1834 p. 228 E. parvituberculahis^ de Blainv. «Dict. tom. 

 37. p. 88, sous le nom d'Æ. microtnbcrciilatus ■ is enumerated under the division D. Espéces réguliéres, 

 de forme un pen variable; les denticules des lignes ambulacraires droites ou arquées de cinq paires de 

 pores au raoins . Accordingl)' it is no doubt wrong when Agassiz and Desor (Catalogue raisonné 

 des Echinides p. 64) enumerates it (referring to the passages quoted above) under their fourth type, 



I) Dictiouuaire des Scieuce.'; naturelles. T. XXXVII. p. SS. (1S25.) 



14* 



