c2 ECHINOIDEA. I. 



quite right. They belong to two different species, most Hkely also to different genera, and none of 

 them has any relation to C. gracilis. 



The specimen from st. 219 has a remarkable form of tridentate pedicellarise ; the blade is long, 

 narrow, with uneven, finely serrate edge, deep and in the lower part filled by a net of meshes. The 

 valve figured on PI. XIV. Fig. 20 is from one of the smaller pedicellarise. I have only found this form 

 of tridentate pedicellarise. The triphyllous pedicellarise (PL XII. Fig. 13) have a well developed cover- 

 plate with few holes; the edge finely serrate. The stalk of the pedicellarise of the common structure. 

 The spicules are large fenestrated plates arranged in two well separated series; the sucking disk well 

 developed. The tube feet are arranged in three series. None of the primary spines on the actinal side 

 are whole, so that nothing can be said of the way in which the point is formed; there is, however, 

 certainly no skin-bag round the point. This species must probably form a separate genus. As, how- 

 ever, no quite sufficient characterization can be given of it here, I shall propose no name for it, but 

 be contented with having pointed out that it has no relation to C. gracilis. 



The specimen from st. 184 has tridentate pedicellarias somewhat recalling those oi Phoniiusoma; 

 but they are distinguished from the latter by the fact that the widenings from the upper end of the 

 apophysis reach quite to the edge of the blade (PI. XIII. Fig. 26); (in Pliormosama they, as stated above, 

 end on the middle of the side of the blade.) The triph)llous pedicellarise are similar to those of the 

 specimen from st. 219. The stalk of the pedicellarise of the common structure. The spicules are 

 lengthened, narrow plates, arranged in 2—3 longitudinal series; no sucking disk is found. On the 

 actinal side the tube feet are arranged in a single regular line (on the abactinal side the arrangement 

 was indistinct in the specimen). All the primary spines on the actinal side are broken, so that the form 

 of the point cannot be decided. — That this species has no relation to C. gracilis or to the specimen 

 from St. 219 is evident. It seems to be nearly related to «/%.» tenuc, and would then have to be 

 referred, together with this latter, to the genus Echinosonia. (See farther down p. 57.) 



Although in the text Agassiz expresses a strong doubt whether the two species here men- 

 tioned, be really 'iA.>-> gracilis, he nevertheless afterwards cites the stations from which they have been 

 obtained, among the localities of this species without adding any interrogation; this way of proceeding 

 is very objectionable — and this is, unfortunately, not the only case. I shall express no opinion 

 whether the specimen(s) from st. 169 is really C. gracilis, as I have not seen it. It is not to l)e relied 

 u])on with certainty, until the pedicellarise etc. have been examined. 



Asf/ifiiosnma,> /cncslratuin Wyv. Thom.son is by Bell (72, 73), and Koehler (229) thought to 

 be synonymous with «^.» hystrix. It has also to be admitted that there is a striking similarity as to 

 habitus between the two species; but a closer examination of the pedicellaria; shows that the question 

 is ,so far from being of one species, that they will even have to be referred to different genera. — 

 There are three kinds of pedicellarite, tetradactylous, tridentate, and triphyllous ones. The tetradac- 

 tylous ones, which have been so excellently described and figured l)y Wyv. Thomson ( Porcupines 

 Echinoidea. PI. LXVII. Figs. 5—6), are something quite unique among the P^chinids, and consequently 

 an excellent character of this genus. Bell (72), to be sure, thinks it to be an abnormal form of pedi- 

 cellarise, as he has not been able to find it in the numerous specimens he has examined. As, how- 

 ever, I have succeeded in finding this form also in A. coriacciim Ag., there can, of course, be no doubt 



