40 DR. P. H. CARPENTER OK CERTAIN POINTS 



of the interambulacra*, and tlie cliaracters of these plates in 

 Bothriocidaris Fahleni and B. globulus respectively seem to me 

 to afford strong evidence that lie is right. In B. PaJileni the 

 plates o£ the interambulacral zones are without tubercles, and so 

 are the supposed genital plates ; but in B. glolulus there are 

 tubercles on the interambulacral plates and also on the so-called 

 genitals. JSTeumayr made no reference whatever to Schmidt's 

 figure of the latter species, which shows eleven plates, not 

 ten, in the periproctal riug, while there are two others which 

 almost enter it. Schmidt t describes the apex iu the following 

 terms : — 



" Die Scbeitelgegencl ist complicirter gebildet, weil die Interradien in Ideinen 

 unregelmassigen langlichen Tafelchen bis zur Aftei-offnung fortsetzen, und die 

 fiinf Scheiteltafelu, die aucb bier auf je Einem Paar der letzten Ambulacraltafeln 

 aufsitzen, den Ereis niebt scbliessen.''' 



Another difficulty in the identification of these terminal inter- 

 ambulacral plates with the genitals of later Urchins is that they 

 occupy a more distal position in the periproctal ring than the 

 radially placed or supposed ocular plates do. In fact, in B. 

 Palileni one of them is excluded from the border of the peri- 

 proctal ring altogether, as the edges of the radials meet inside it. 

 Neumayr was fully aware of this t ; but it does not seem to have 

 made him in any way doubt the correctness of his identification 

 of these plates as genitals : — 



" Wir seben also, dass bier ein Verbaltniss berrsebt, welcbes demjenigen bei 

 jiingeren Seeigeln gerade entgegengesetzt ist. Bei der Annahme zweier fiinf- 

 zabbge Kranze wilrden bier die Augentafelcben deninneren, die Genitaltafelcben 

 den aiisseren derselben bilden. Eine solcbe Umkebrung ist eine absolut Un- 

 moglicbkeit." 



"With the last remark I am quite in accordance. But con- 

 sidering that there are other strong reasons against Neumayr's 

 novel interpretation of these plates as the genitals, I cannot 

 agree with him in attaching so much importance to the condition 

 of BofJiriocidaris as to make it altogether outweigh the evidence 

 afforded by the comparative anatomy and embryology of the 

 Echinoderms generally. Even if it be granted that Neumayr's 



* jLoc. cif. pp. 39, 41. 



t Loc. cit. p. 41, Taf. iv. fig. 2 b. 



j Oj} crY. p. 364. 



