4 8 



ECHINOIDEA. II. 



The basal part is rather large. In the larger 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' nm long. - The 

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

 IX. Fig. 22) are short and broad, reminding one, indeed, very much of the ophicephalous pedicellarioe 

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

 these features they resemble the short broad form of tridentate pedicellarise in Urcc/iinus naresiaintx. 

 and perhaps they ought really to be regarded as trideutate pedicellariae. The other form (PL XI. Figs. 

 7, 10) has very elongate, narrow valves, 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 way down the sides, rapidly diminishing in size. 

 There is a simple oval deepening in the widened outer part. One of the valves is considerably longer 

 than the two others, and this one alone has an arc developed below 7 the articular surface. The stalk 

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

 they are, indeed, very conspicuous objects, and by no means rare, but they seem to occur only on the 

 abactinal side, whereas the short, globular form seems to occur only 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 Cystechinus crassus described by 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 Cystechimts this objection seems a little curious, since Professor 

 Agassiz himself associates the equally thick-plated form from St. 205 with Cystechinus and even 

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



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

 found four kinds of pedicellarise, viz. globiferous, tridentate, ophicephalous and triphyllous. The globi- 

 ferous pedicellariae (PI. IX. Fig. 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 found only one specimen of this kind of 

 pedicellaria in the dried fragments from St 133; there is no trace of a thick investing 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 possibly be referred is the rostrate) '. The tridentate pedi- 

 cellariee are of two kinds; one has simple, leaf-shaped valves (PI. IX. Fig. 20), narrowed only for a 

 short space below, in the smaller ones joining along their whole length ; the edge is very finely serrate. 

 The largest ones seen are ca. o-8 mm (head). The other form (PI. IX. Fig. 23) is short, coarse; it was 

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

 tridentate pedicellarise of Urcch. narcsianus, 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 Urech.naresianus must .also be regarded as a tridentate pedicellaria. -- The small large- 

 headed* pedicellaria of Cystech. clypeatus, figured in the Challenger -Echinoidea, PI. XLJI. Figs. 1516 



1 By the name rostrate I designate the kind of pedicellariae named die schnabelforniigen by Doderlein, as well 

 as those named die kochl6ffelforinigen><, which are only a modification of the former type, as pointed out by Doderlein; 

 these two forms Professor Doderlein also designates by the name < laternenforinige tridentate pedicellarise. (Echinoidea d. 

 deutschen Tiefsee-Exp. p. 73). 



