US' THE MORPHOLOaT OF THE CTSTIDEA. 51 



of the Blastoid Catalogue and also by Messrs. "Wachsrautli and 

 Springer. It is quite refreshing, however, to find him speaking 

 of " the central part of the ambulacral area or mouth." Why 

 cannot he always do so ? 



Miller likewise gives a good figure showing the summit-plates 

 in his new species Garyocrinus Indianensis *. The six central 

 plates, orals, as I regard them, are plainly visible ; but the two 

 anterolaterals are separated from the interradials (13, 18) by 

 smaller plates, instead of coming into direct contact with them, 

 as in the specimens of C. ornatus kindly lent me by Mr. Wachs- 

 muth, one of which I have figured (PI. I. fig. 14). I do not re- 

 remember that the latter condition has yet been described in 

 Garyocrinits, though it possibly presents itself in the specimens 

 figured by Hall t and Zittel %. It is a point of some importance 

 as regards the homologies of these summit-plates, for in Stepha- 

 nocrinus, Elceacrinus, and in some species o^ Platycrinus, the 

 orals also come into direct contact with the interradials. In 

 Mr. "Wachsmuth's specimen the tegmen is much depressed along 

 the lines of these two anterolateral interradials, and Miller says 

 that in C. Indianensis it is " depressed, convex, and sunken 

 between the arm clusters so as to give it a wavy surface. The 

 central plate is large, heptagonal ; it is surrounded by seven 

 plates that cover nearly the whole summit. Two of the seven 

 plates curve upward and surround two-thirds of the prominent 

 azygous opening." The central plate, together with five of the 

 seven around it, are the orals, the other two belonging to the 

 anal system, just as is shown in Hall's figures of the summit of 

 C ornatus, or in Mr. Wachsmuth's specimens. Miller, however, 

 describes the " vault " of (7. Indianensis as " diff'erent from that 

 of C. ornatus, the structure of which Wachsmuth thought was 

 generic." But the only point of difference is that in some indi- 

 viduals of G. ornatus a third anal plate comes up into line with 

 the other two, just behind the posterior oral ; and this led Wachs- 

 muth to describe the latter as surrounded by eight plates §, while 

 Miller only finds seven in G. Indianensis. This difi'erence, how- 

 ever, is certainly not of specific value, and I am inclined to think 

 that the same may be said of the other characters on which Miller 

 founded the species Garyocrinus Indianensis. 



* Bid. p. 19, pi. Y. fig. 10. 



t ' PalEeontologj' of New York,' vol. ii. pi. 49. fig. 1 v, pi. 49 a. fig. 1 e. 



\ ' Pal^eontologie,' Ed. i. p. 419, fig. 295 b. § See supra, pp 19, 20. 



