404 Dr. P. H. Carpenter on the 



greater part, of the ventral side is abactinal, and this we consider 

 one of the best distinctions between the two groups." 



But since this somewhat extensive generalization is very 

 largely based upon the authors' totally erroneous ideas 

 respeeting the structure of the summit in the Crotalocrinidge, 

 I do not believe that it expresses such an extremely important 

 distinction between the Neocrinoids and the Palajocrinoids as 

 they endeavour to make out. This passage, liowever, is 

 employed as an argument to prove that the plates hitherto 

 considered as orals in the permanent larval forms Ilaplocrinus 

 and AUagecrinus * are not orals at all, but calyx-interradials 

 which cover in the disk and, in the case of AUagecrinus, the 

 summit-plates as well. But as the " extravagant develop- 

 ment " of the interradials in the Silurian Grotalocrinus turns 

 out to be an utterly erroneous theory, which has no other 

 foundation than a complete misconception of Angelin's figures 

 on the part of Messrs. Wachsmuth and Springer, tliey will 

 have to seriously reconsider a great deal of the reasoning 

 which they have based upon it respecting the homologies of 

 the summit-plates in Neocrinoidea and Palajocrinoidea re- 

 spectively. I have no intention, however, of taking up this 

 discussion again at present, and I will pass on to a few words 

 on the classification of Palseocrinoids. 



Wachsmuth and Springer established the suborder Articu- 

 lata " to include the group formerly defined by us under the 

 family name Ichthyocrinidge, with the addition of Grotalo- 

 crinus and Enallocrinus, which possess in a remarkable 

 degree some of the most characteristic features of the group ;^' f 

 and they say further on — " we think it altogether probable 

 that the general plan of the ventral structure for the Articulata 

 generally is expressed in that of Grotalocrinus ^ 



I have endeavoured to show, however, that their theory as 

 to the ventral structure of Grotalocrinus is altogether incorrect, 

 owing to a faulty interpretation of Angelin's figures and to 

 their want of personal acquaintance with the actual fossils. 

 But the supposed existence of a flexible vault in Grotalo- 

 crinus is one of the reasons adduced by Wachsmuth and 

 Springer for placing this genus among the Articulata, viz, 

 those Crinoids " in which the plates of the test are united by 

 loose ligaments or muscles, and in which they are somewhat 

 movable" |. So far as my knowledge goes, however, it has 

 yet to be proved that there was any such articulated arrange- 



* "On Allagecriims, the Representative of a new Family from the 

 Carboniferous-Limestone Series of Scotland," Ann. & Mag. Nat. Hist. 

 1881, ser. 5, vol. vii. pp. 285, 286. 



t ' Revision,' part iii. p. 140. J Ibid, p, 6. 



