284 Bihliograpliical Notices. 



we have italicized in the following manner : — " It is very significant 

 that Etheridge and Carpenter also found in Allagecriaus ' at the 

 central end of one or more of the plates faint tubercles ; ' " and they 

 then make use of their version to argue against the oral nature of 

 these plates. " Whether these represent the tubercles which we 

 discovered upon the surface of the interradials in Cijathocrinus multi- 

 radiatus* (pi. iv. fig. 2), we are, of course, not prepared to assert 

 with certainty, but it is worthy of note that Carpenter regards the 

 latter ' as the conical openings in Onmatocrhius Norwordi' (!), and 

 it is very possible that they are the same thing in all three groups, 

 which would prove better than anything else that the plates bearing 

 them arc not orals but interradials. The tubercles in AUar/ecrinus 

 are evidently of structural value, but as there is but one figured, 

 although the description speaks of one to each plate, and this is 

 located laterally in one specimen and centrally in the other, all 

 interpretations by us must necessarily bo more or less problematical. 

 We are inclined, however, to believe that the lateral one (fig. 5), 

 in analogy with Hajylocrinus, represents the anal opening, i. e. the 

 larger tubercle in Granatocrimis, and the central one, if it exists at 

 all, the central piece." 



The whole point of this argument in the comparison of Allagecrinus 

 with Ci/atJiocrinus Oilesi and the tubercles upon each of its five inter- 

 radials depends upon the supposed fact that " the description speaks 

 of one to each plate." But all that the description says is that a 

 faint tubercle may be present on one or more of the plates ; and of 

 the nine figures given of the summit only four show any trace of 

 tubercles at all, and then of but one only, as Wachsmuth and 

 Springer admit. Under these circumstances we should like to know 

 why the tuljercles are " evidently of structural value." 



Furthermore, it was explicitly stated that there is no trace of an 

 anal opening directly piercing an oral plate, as has since been 

 described by Wachsmuth and Springer in Haplocrituis. \ very large 

 series of specimens was examined, and special attention was directed 

 both to this point and to the possible presence of a central plate ; 

 but the result in both cases was a negative one. Wachsmuth and 

 Springer tell us, however, on p. 53, that the central plate " is the 

 only summit plate which is represented in every Pala^ocrinoid." This 

 seems to us to be rather a bold assertion. There are many forms in 

 which the summit is as yet unknown; while, though well defined in 

 Oulicocrinus,Fisocrimis, Allagecrinus, and two species of Haplocrinns, 

 it has never yet been found to contain a central plate. The analogies 

 of Stephanocrhms and Ela'acrhius among the Blastoids, and of 

 Oliiptospluerites and Caryocrinus among the Cystids, show that the 

 presence of a central actinal plate is not a constant character in 

 either group. Why, then, should it be described as such in the Palteo- 

 criuoids, when there is at least as good evidence to the contrary as in 

 the undisputed cases of Ste]>lianocr'mus and Glyptosp)hcerites'i 



We cannot but admire the courage of Messrs, Wachsmuth and 



* It appears from a reference to the explanation <if }>!. iv. fig. 2 that 

 the speciKc name midtiradiatus should read Gdesi. On the other hand, 

 according to the explanation of fig. G, C. midtiradialns, on p. 22, should 

 read C ^nnltihrachiatiis as on p. 65. 



