ECHINOIDEA. I. 107 



Primary tubercle on every ambulacral plate; the globiferous pedicellarirc with 



2—4 teeth on either side, the edges not connected St. horridus. 



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



ambulacral plate St. magellanicus. 



Echinus mtltarzs, microtuberculatus, and angulosus form a separate group chiefly characterized 

 by the globiferous pedicellarise (PI. XVII. Figs. 1, 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 pedicellariae is found in Sterechinus horridus (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 iu Ech. miliaris 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 following characters of the separate species must be pointed out. In Ech. miliaris the 

 buccal membrane is covered by large, thick fenestrated plates. The globiferous pedicellarise 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 siuuations are again finely serrate; the small teeth form no transverse 

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

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

 culafus the ocular plates are shut off from the periproct, in E. angulosus the two (three) reach to the 

 periproct; 110 distinct central plate. 



Ech. microtubcrculatus agrees exactly with miliaris in the structure of the pedicellarise; it is 

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

 the edge. The plates 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 plates inside of the buccal plates are constructed in this way. Otherwise it is distin- 

 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. microtubcrculatus 1 ) it is said: ambulacres a denticules tres-arquees et composees de six paires de 

 pores >; in Blainville's Manuel d'Actiuologie > 1834 p. 228 E.parvitubercalatus, de Blainv. «Dict. torn. 

 37. p. 88, sous le uom d'E. microtubcrculatus is enumerated under the division D. «Especes regulieres, 

 de forme un peu variable; les denticules des lignes ambulacraires droites on arquees de cinq paires de 

 pores an moins . Accordingly it is no doubt wrong when Agassiz and Desor (Catalogue raisonne 

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



') Dictionnaire des Sciences uaturelles. T. XXXVII. p. SS. (1825.) 



14* 



