64 



ECHINOIDEA. II. 



other side, evidently tlie inner plate of interambnlacra i and 4 (PI. VIII. Fig. i), as it is also found 

 sometimes in P. Jeffreysi. Upon the whole the structure of the actinal .side, labrum, sternum, episternum, 

 the two ambnlacra of the bi\-iuui and the postero-lateral interanibukicra agree very nearh" with that 

 of /'. fefreysi. Tlie periproct differs a little in outHne from that of Jeffreysi. being more elHptical, not 

 abruptly widened in the upper part as in that species. The piates surrounding the periproct are 5. a. 

 6_8 and b. 7—9; this holds good also for yonnger specimens, whereas in smaller specimens of P. Jef- 

 freysi Itill at least a size of 30'""') there are 4 epiproctal piates on each side (5.3.5 — 8 and b. 6— 9) (in 

 larger specimens there are onh- three epiproctal piates as in P. Wandeli. the lower pair being shut 

 off from the periproct). The apical system (PI. VIII. Figs. 2, 7) as in Jeffreysi, perhaps a little closer 

 to the anterior border than in that species. I have found a case of the genital piates being distinct 

 (PI. VIII. Fig. 2) as found e.xceptionally by Loven in Jeff'reysi (in that species I have not met with 

 such a case). 



The tnberculation shows some difference from P. Jeffreysi. The linear arrangement of the pri- 

 mary- tubercles is in larger specimens more prominent than in that species. The interambnlacral piates 

 at the front sides (posterior series of interambnlacra 2 and 3) each bear two prominent parallel or 

 posteriorlv a little diverging, series of primary tubercles; on the uppermost and lowermost 2—3 piates 

 of this series the linear arrangement of the tubercles is iudistinct. The part of these piates, which is 

 bent over on the front edge, bears only few, irregularly arranged priniar>- tubercles, as is also the case 

 with the other piates on the front. The following two series of piates (ambnlacra II and IV, a. b.) bear 

 a series of primary tubercles each. Also the following interambnlacral piates show a tendenc}- towards 

 a serial arrangement of the tubercles. In these series the tubercles always increase in size from before 

 towards the posterior end, the hinder one being the largest. It is onl\- the piates on the sides of the 

 test which have the tubercles thus serially arranged. The rest of the test has like P. Jeffreysi only 

 irreo-ularlv scattered primary tubercles, somewhat less nnmerous, however, than in that .species. The 

 miliar\- tubercles are upon the whole less nnmerous than in Jeffreysi, the test looking more sinooth 

 than is generaliv the case in that species. The sutures are not elevated as in Jeff'reysi. — Though the 

 serial arrangement of the primar>- tubercles is much more prominent in P. Waiideli than \\\ Jeffreysi. 

 when larger .specimens are compared, it must be conceded that in smaller specimens the serial arrange- 

 ment is almost equally developed in both species. 



The primary spines of the abactinal side are ver}- long, especially those of the anterior series 

 of the antero-lateral ambnlacra and those of the interambnlacral piates on the front edge, and — ni 

 accordance with the size of the tubercles — the posterior spine of each series is the longest. The 

 longer of these spines reach from the anterior end of the test to the periproct, thus reaching more 

 than two thirds of the length of the test. They are cnrved and bent backwards, lying rather close to 

 the test; generally they are strougly thorn>-, especially along the con\ex side, which gives them a 

 characteristic lustre. Sometimes they are irregularly curved at the point. (PI. \'. Figs. i, 3, 5. PL XI. 

 Fig. 36). These long spines give this species a very characteristic appearance, differing highly from 

 P. Jeffreysi in which species the spines are much shorter, smooth, and generalh- not bent backwards 

 over the te.st. (Comp. PI. V. Figs. i, 3, 5 with PI. V. Figs. 19, 21, 23). — The spines of the actinal plastron 

 (PI. XI. Fig. 35) are flattened at the point, like those oi Jeffreysi, and likewi.se those within the invagi- 



