366 p. HERBERT CARPENTER. 



alternate with them. This is precisely the relation of the 

 " second parabasals " of Marsupites (fig. ui, 3, 3) and of 

 the parabasals generally in all those Crinoids (fig. vi, 3, 3) 

 in Avhich they ai-e present. Many reasons which 1 cannot 

 enter into here, though I shall shortly state them fully else- 

 Avhere, have led me to the conclusion that the so-called 

 " parabasals " of the Palaeozoic Crinoids are really the basals. 

 According to the present system of nomenclature, two dis- 

 tinct sets of plates are termed basals in this group. In 

 JPlatycrinus and in all the others in which there are only 

 two sets of plates in the calyx, the lower ones resting on the 

 uppermost stem segment, were called basals by M tiller.^ 

 This was perfectly correct, for their position is interradial, 

 and they correspond in every respect to the basals of Penta- 

 crmus, the calyx of which genus was taken by Miiller as a 

 type, on which he based his analyses of the calyx in all the 

 other Crinoids. On the other hand, the plates which 

 Miiller called basals in Cyathocrinus (fig. vi, 2, 2), because 

 they rest upon the uppermost stem segment, are radial in 

 position, Avhile the "parabasals" (fig. vi, 3, 3) which 

 intervene between them and the radials (fig. vi, 4, 4) 

 alternate with both series and are therefore interradial. It 

 is these plates which I regard as representing the basals of 

 the other Crinoids. Miiller assumed that the basals must 

 always rest upon the uppermost stem segment, and hence 

 fell into an error in which he has since been followed by 

 every one but Bey rich. In the calyx of Encrinus, as shown 

 by Beyrich,- the true basals (fig. iv, 3, 3) homologous with 

 those of the other Articulata, are separated from the upper- 

 most stem segment by a ring of five small phites (fig. iv, 

 2, 2) which alternate with them and are therefore radial in 

 position. I shall shortly show that these second or under 

 basals are also present in the calyx of Pentacr'mus hriareus 

 and of P. subangularis, though they are absent in the other 

 Pentacrini. I believe them to be homologous with the 

 "first parabasals" of Marsupites (fig. iii, 2, 2), and with 

 the plates which have been hitherto regarded as basals in 

 Cyathocrinus (fig. vi, 2, 2), Potcriocrinus, liliodocrinus, 

 and the other Palccozoic Crinoids in which the so-called 

 parabasals are present. 



Beyrich^ has already pointed out the resemblance of the 

 two circlets of basals iu Encrinus to the two series of plates 



' ' Pentac/inus,'' loc. cit., p. 31. 



'^ " Ueber die Criuoidceu des Muschelkalks," ' Abliandlungeu der Berlin 

 AkaJemie,' 1857, p. 13. 

 ^ Loc. cit., p. 13. 



