,o ECHINOIDEA. II. 



4» 



The basal part is rather large. In the laro;er ones the valves join along about the outer half, in smaller 

 ones they join a longer way down; in the largest specimens seen the head is o-6'"™ long. — The 

 ophicephalous pedicellarise are ver\- peculiar. One form has an almost globular head; the valves (PI 

 IX. Fio-. 22| are short and broad, reminding one, indeed, ver\- much of the ophicephalous pedicellarite 

 of the Echinina; the arcs are, however, not distinctly developed, and the stalk is not cup-shaped. In 

 the.se features the\- resemble the sliort broad form of tridentate pedicellarire in L'rrc/iimts narrsiaiius. 

 and perhaps they ought really to lie regarded as tridentate pedicellariie. The other form (PI. XI. Figs. 

 7, lo) has ver\- elongate, narrow vahes, with a terminal widening (the blade); the long narrow part 

 represents the apophysis, whereas the basal part is not distinctly developed. The outer edge of the 

 blade forms a series of large teeth, continuing a little wa>- down the sides, rapidh diminishing in size. 

 Tliere is a simple oval deepening in the widened outer part. One of the \alves is considerabh- longer 

 than the two others, and this one alone has an arc developed below the articular surface. The stalk 

 is cup-shaped above, otherwise compact. The length of the head of these pedicellariae is ca. i""", and 

 they are, indeed, ver\- conspicuous objects, and b\- no means rare, but the\- seem to occur onl\- on the 

 abactinal side, whereas the short, globular form seems to occur onl>- on the actinal side. — Regarding 

 the structure of the test of this form, I can only say that the plates are very large and the pores simple. 

 The fossil Cystechimis crassiis described b\- Gregory (Op. cit) must probably be nearest related 

 to this thick-plated species. Since neither the apical or the actinal system of this fossil form is known, 

 it was perhaps somewhat hazardous to associate it with this genus, as maintained by Agassiz; but 



when Professor Agassiz says that the great thickness of the plates would seem to preclude the 



association of this species with Cystcchinusy this objection seems a little curious, since Professor 

 Agassiz himself associates the eqnalh- thick-plated form from St. 205 with Cystrclii>ius — and even 

 includes it in the same species with the exceedingh- thin-plated form from off Tristan d'Acunha. 



In the fragments of Cystrcliinns clypcatus from St. 133 and 334, the thin-plated form, I have 

 found four kinds of pedicellariae, \iz. globiferous, tridentate, ophicephalous and triph>llous. The globi- 

 ferous pedicellariae (PI. IX. P'ig. i) are very peculiar; the blade is an almost closed tube, with a narrow 

 slit along the inner side, and ends in a single hook. I have fotmd ouh- one specimen of this kind of 

 pedicellaria in the dried fragments from St. 133; there is no trace of a thick in\esting skin, as might 

 be expected in a globiferous pedicellaria; I think, however, that it is really a globiferous pedicellaria 

 (the only other kind to which it might pos.sibly be referred is the rostrate) '. The tridentate pedi- 

 cellarice are of two kinds; one has simple, leaf-shaped vahes (PI. IX. F'ig. 20), narrowed only for a 

 short space bolow, in the smaller ones joining along their whole length; the edge is \er\' fineh' serrate. 

 TIk- largest ones seen are ca. o-8""" (head). The other form (PI. IX. b'ig. 23) is short, coarse; it was 

 found especially developed in some fragments from St. 133. This form recalls the short thick form of 

 tridentate pedicellarite of Uncli. naresianus. and as all intermediate stages occur between the short, 

 robust form and the long and slender form of tridentate pedicellarise, it seems to give the proof that 

 this form in Urcch. naresianus must also be regarded as a tridentate pedicellaria. — The .small large- 

 headed pedicellaria of Cystech. clypcatus^ ^\o\\x&^ in the Challenger -Echinoidea, PI. XLII. Fig.s. 15 -16 



■ By the name «rostrate» I designate the kind of pedicellariiL named «die schnabelfiirniigen by Doderlein, as well 

 as those named «die kochliiffelformigen v, which are only a modification of the former type, as pointed out by Doderlein; 

 these two forms Professor Doderlein also designates by thu n.inn.- latcnienforniige tridentate ]Hdiccllarix. (Kchinoidca d. 

 deiitschen Tiefsee-Exp. p. 73). 



