KCHINOIDEA. II. 



67 



spines. In these characters P. )iiiru>ida agrees witli /'. laguncula, and Agassiz ( Cliallenger -Echini 

 p. 137) is certainly right in stating that this species is closely allied to P. i/iirandaK Also the /■■. Tanneri 

 is regarded by Agassiz as closely related to P. lagioicnla: it is, howex'cr, not clear from his otherwise 

 (regarding the strnctnre of the test) vers- elaborate description and fignres of this species, whether it 

 agrees with laguncuLa (and iniranda) in the shape of the spines and the de\elopnient of the front ten- 

 tacles. Of the spines it is only said : the primary radicles on the flanks of the test are also longer, 

 while in P. lagiincula and P. miranda the\- are somewhat spathiform (Pan. Deep-Sea Ech. p. 132). The 

 front tnbe-feet are not mentioned at all. Having received a specimen of P. Tnnncri from the U. S. 

 National Mnsenm I can state that the spines are not widened towards the point, whereas the frontal 

 tnbe-feet are really rather large and conspicnons The pedicellarite do not afford any proof of a close 

 relationship between P. Taiincri and lagiiiicnla. In the former species I ha\'e fonnd onl\- rostrate 

 pedicellaria: with rather slender \alves (PI. XI. Fig. 11) and small tridentate pedicellaricc of the same 

 form as in P. Jcffrcysi. 



In /-*. lagiiiicnla (examined in the P>ritish Mnsenm) I have found (in a specimen from St. 232) 

 globiferons pedicellarise with the valves ending in two or three long teeth, resembling closely those 

 of P. carina fa (comp. PI. XI. Figs. 16, 22), ophicephalous pedicellarise with rather elongated, slender 

 valves (PI. XI. Fig. 12) — (differing considerably from those figured in the Chall. -Ech. PI. XLIII. 18 

 — 19 under the name of < Clypeastroid-like pedicellarise, so much, indeed, that the\- can scarcely be- 

 long to the same species) — and two forms of tridentate pedicellaria;, viz. the usual small form, which, 

 however, here occurs also with the apophysis continuing into the outer edges of the blade, and a 

 larger form with long and slender valves with the blade almost flat (PL XI. F'ig. 33), the outer edge 

 very finely serrate. (This form differs so much from the pedicellarise of the other species that it ma\- 

 perhaps be suggested not to belong really to this species). Of rostrate pedicellarise I have found onl\- 

 one small specimen, which does not differ essentially from those of P. Tanneri. vSmall spicules, in the 

 shape of fenestrated plates are found in the large frontal tube-feet. 



The form figured in the Challenger -Echinoidea PI. XXXI. 7 — 11 and mentioned (p. 138) as 

 younger specimens of P. lagitiinila showing considerable variation in the outline can hardly be the 

 same species as that figured in the same Plate, Figs, i — 6, which must be taken as the type of the 

 species. The latter specimen was 22""^, that represented in the figure 7 — 11 was 12™"' in length. It 

 seems hardly conceivable how so great a difference in the shape of the test could be due mereh' to 

 changes during growth, and a growth only from 12 to 22""° in length. This is made even more un- 

 likely when we learn ( Chall. -Ech. p. 138) that some of the specimens with narrow anal snout char- 

 acteristic of the smaller specimens measuring from 12 — 16""" were nearly 19""" in length . The con- 

 clusion seems quite inevitable that this form with the narrow anal snout is a distinct species, which 

 will perhaps prove identical with P. Tnnin'ri. The material preserved in the British Museum does not 

 give the solution of the question, since no specimen is found which can with certainty be recognized 

 as belonging to the narrow type (Chall. -Ech. PI. XXXI. 7 — 11). Specimens of the broad type, the real 

 P. lag-iinaila are preser\ed from St. 232 and St. 191 (the latter are badh- crushed, but can, howe\er, be 

 recognized as belonging to this form); from ,St. 169 small fragments only are preserved, which cannot 

 be recognized as belonging to either of the forms, and the same is the case with the anterior ends 



9* 



