IN THE MOEPHOLO&T OP THE CTSTIDEA. 29 



which does not necessarily exclude that advanced by Cuenot. So 

 far as the Crinoids are concerned, it seems to me not unlikely 

 that the structure at the ventral end of the ovoid gland, which I 

 have described as the labial plexus *, or at any rate the specially 

 modified portion of it which forms the spongy organ, may be ne- 

 phridial in function. It is most largely developed round the 

 hinder part of the peristome, between it and the anus ; while the 

 inner ends of some of the water-pores open in close proximity to 

 it, and may even be in connection with it, as described by Perrier f. 



Wachsmuth and Springer have recently suggested that the 

 apparently poriferous plate between the moath and anus of Ci/a- 

 thocrinus is a madreporite $, and their view is supported by the 

 fact of this being the primary position of the water-pore in the 

 larval Echinoderm. 



Under these circumstances there is much reason to think that 

 Yolborth § was right in suggesting that the plicated triangular 

 structure between the mouth and genital pore of G-lyptosphcBra 

 Leioclitenlergi may be a madreporic plate. Quenstedt || says 

 that it seems to consist- " aus drei welligen Klappen, .... und 

 niemals fehlt." It is well shown in the two figures of the Eussian 

 species in Angelin's ' Iconographia '•[[, and is explained by Loven as 

 the " rhombus " ; but there is no indication of it in Zittel's figure 

 of the same tyj)e **, nor is it mentioned in his generic description. 

 Steiumann ft figures it, however, and compares it to a madrejDorite, 

 Barrande ++ compared it, and I think rightly so, to the slit-like 

 opening just behind the peristome of Aristocystis (PL I. figs. 12, 

 13) ; while the ' Nature ' reviewer extended the comparison to 

 the opening at the edge of the peristome, just above plate 18, in 

 the British JEchinoencri?ius, which Forbes had regarded as the 

 anus §§. There would seem, however, to be something wrong 

 about Eorbes's description of this opening as being on the right 



* ' Eeport upon the Crinoidea of the ' Challenger ' Expedition,' 1885, p. 98. 



t ' Memoire sur I'Organisation et le Developpement de la Comatule de la 

 Mediterranee,' 3>"<= Partie, Nouv. Arch, du Museum, 3'^ serie, t. ii. (Paris, 1890) 

 p. 69. 



J " The Perisomic Plates of the Crinoids," Proc. Acad. Nat. Sci. Philad* (1890 

 p. 358, pi. ix. fig. 7. 



§ 'Ueber die russischen Sphaeroniten,' p. 29, Taf. x. fig. 1. 



II ' Encriniden,' p. 694. ^ Op. cit. tab. xi. figs. 1, 2. 



** ' Paleontologie,' Ed. i. p. 416, 



ft Op. cit. p. 178. \X Op. cit. p. 45. 



§§ Loc. cit. p. 485, pi. xviii. fig. 3. 



