ECHINOIDEA. II. 67 



spines. In these characters P. miranda agrees with P. laguncula, and Agassiz ( Challenger -Echini 

 p. 137) is certainly right in stating that < this species is closely allied to P. miranda^. Also the P. Tanneri 

 is regarded by Agassiz as closely related to P. laguncula; it is, however, not clear from his otherwise 

 (regarding the structure of the test) very elaborate description and figures of this species, whether it 

 agrees with laguncula (and miranda) in the shape of the spines and the development 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. laguncula and P. miranda they are somewhat spathiform> (Pan. Deep-Sea Ech. p. 132). The 

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

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

 tube-feet are really rather large and conspicuous The pedicellariae do not afford any proof of a close 

 relationship between P. Tanneri and laguncula. In the former species I have found only rostrate 

 pedicellariae with rather slender valves (PI. XL Fig. n) and small tridentate pedicellarise of the same 

 form as in P. Jeffreysi. 



In P. laguncula (examined in the British Museum) I have found (in a specimen from St. 232) 

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

 of P. carinata (comp. PI. XL Figs. 16, 22), ophicephalous pedicellariae with rather elongated, slender 

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

 19 under the name of Clypeastroid-like>> pedicellariae, so much, indeed, that they can scarcely be- 

 long to the same species) and two forms of tridentate pedicellariae, 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 (PI. XL Fig. 33), the outer edge 

 very finely serrate. (This form differs so much from the pedicellariaa of the other species that it may 

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

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

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



The form figured in the Challenger --Echinoidea PI. XXXI. 711 and mentioned (p. 138) as 

 younger specimens of P. laguncula 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 tnm , that represented in the figure 7 n was i2 mm in length. It 

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

 changes during growth, and a growth only from 12 to 22 mm 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 i6 mm were nearly ig" 1 in lengths. 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. Tanneri. The material preserved in the British Museum does not 

 give the solution of the question, since uo specimen is found which can with certainty be recognized 

 as belonging to the narrow type (Chall.-Ech. PI. XXXI. 711). Specimens of the broad type, the real 

 P. laguncula are preserved from St. 232 and St. 191 (the latter are badly crushed, but can, however, 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* 



