ECHINOIDEA. II. 47 



(Panamic Deep-Sea Ech. p. 163) to tlie genus PilniiaticJiiims established tliere for Cystech. Rathbuni. 

 — A few remarks 011 the forms mentioned above maj- be given liere. 



Cystcchiuiis cLypeatiis. In the description of this species ( Cliall. -Ech. p. 149) Professor Agassiz 

 remarks that in the specimens from the greater depths |ca. igoo fathoms) the test is niucli thinner 

 than in the fragments which are found near the 1000 fathom Hue . This mav perliajss be true for 

 other species (Agassiz refers to Pourtalrsia. Cystechiuiis and Urrchiiiiis), though I do not see an\' 

 such difference among the specimens of U. naresianns from the Ingolf-; but as for C. clypeatns the 

 difference in the thickness of the test is in an\- case not alone due to the different depth at which 

 the specimens lived, but also to their being different species, as I can state after having examined 

 the fragments preserved in tlie British Museum; the pedicellariæ differ so considerabh- that it seems 

 quite impossible that they can belong to the same species. Also the strncture of their apical sys- 

 tems will probably be found to differ considerabh'. In the description it is said: The abactinal 

 system closely resembles that of Cysfcchinus Wyvillii: the genital piates are, however, proportionalh- 

 larger, the left anterior and the right posterior far exceeding the others in 

 size, and extending entirely across the abactinal area, the whole central part 

 of which is formed by the junction of the genital piates . But the figure, PL 

 XXXV. b. 10, is, as will be seen, not in accordance with that description; the 

 left anterior and right posterior genital piates do not exceed the others in 

 size or extend entirely across the abactinal area, and the whole central part 

 is not formed by the junction of the genital piates, the large ocular piates 

 of the anterior paired ambulacra separating widely the anterior and posterior 

 genital piates. — Among the fragments of Cystccltiims clypcatus preserved in 

 the British Museum the apical system is found in those from St. ^^4, which _.,,., ^ , 



^ ■> OOT^' Fig. 5. Apical system of 



belong to the thin-plated form. This apical system does not agree, however, Cystechiuus dypeatus iSt. 

 either witli the description or the figure (PI. XXXV. b. 10) as will be seen from 



the sketch given here (Fig. 51. (It may be remarked that tliis figure was made free hånd, withont a 

 camera, so that the form of the piates ma}- not be quite correct, but in the main features the figure 

 is correct.) In the fragments from St. 133, which evidently belong to the same species as those from 

 St. 334 (both these stations are near Tristan d'Acunha), onl\- the two jDosterior apical piates, together 

 with some of the piates behind them, are preserved; this part agrees with the figure in the Chal- 

 lenger -Echini, which tims seems to have been made after this specimen. Whether the whole figure is 

 correctly drawn can no longer be seen. — Among the fragments from St. 205 (off Luzon, in the China 

 Sea)', the thick-plated form, no trace of the apical system is found. 



On the fragments of the thick-plated form (St. 205) I have found three kinds of pedicellariæ, 

 viz. tridentate and two kinds of ophicephalous pedicellariæ. Unfortunately, no globiferous pedicellariæ 

 were found; they will probably also be very characteristic, as is the case with the ophicephalous. The 

 tridentate pedicellariæ (PI. IX. F'igs. 14, 28) have a simple, leaf-shaped blade, somewhat narrowed in the 

 lower part. The edge is thick, onl\- faintly serrate, often with a larger tooth at the point; in the larger 

 ones there is, generally, a wingshaped lateral widening below the edge in the lower part of the blade. 



' .\loue this very wide distance between the stations might beforehand raise sonie doubt of these fonus being the 

 same species. 



