32 BULLETIlSr 115, UNITED STATES NATIONAL MUSEUM. 



DOLATOCRINUS GRANDIS Miller and Gurley. 



Plate 7, figs. 1-8; plate 9, fig. 5; plate 10, fig. 2, 



Cacahocrinites sculptus Troost MS., Proc. Amer. Assn. Adv. Sci., 1850 (read 



1849), p. 60; Bull. CA, U. S. Nat. Mns., 1909, p. 55. 

 Dolatocrinus fjrandis Miller and Gurley, Bull. 4, 111. St. Mus., 1894, p. 14, 



pi. 2, figs. 4-6; pl.'l, fig. 8 fas D. vmrsM).—Woo-D, Bull. 64, U. S. Nat. Mus., 



1909, p. 55, pi. 12, fig. 2. 

 Dolatocrinus excavatns Wachsmuth and Springer, N. A. Crin. Cam., 1897, p. 



321, pis. 25, fig. 1, and 26, figs. 7, 8.— Rowley in Greene, 1903, pp. 134, 145, 



191. 

 Dolatocrinus fjrandis, var. incarinatus Rowley in Greene, 1903, p. 112, pi. 35. 



figs. 1-3. 

 Dolatocrinus marshi Rowley in Greene, 1903, p. 159, pi. 47, figs. 7, 8. 

 Dolatocrinus fossatus Rowley in Greene, vol. 2, 1906, p. 7, pi. 3, figs. 1-3. 



This splendid species is most appropriately named, not only on 

 account of its large size, but of the decisive way in which it stands 

 out among all species of the genus, so perfectly distinct that there is 

 no other with which it could be confused. The specimen upon 

 which it was described, while excellent in some respects, was not in 

 condition to exhibit all the characters, especially those of the base, 

 and it is therefore necessary to give some further illustrations. 



The species is remarkable for the extent to which the base is exca- 

 vated and indented by the huge column facet. Wliile the calyx wall 

 curves inward to form a broad concavity on the dorsal side, within 

 this there is sunken a large and very deep pentagonal pit involving 

 the whole of the radials, the upper margins of which form the angular 

 edge of the pit, and at the bottom of which, at about the level of the 

 arms, lie the rather small basals, buried under at least half an inch of 

 column when in place. 



It is also remarkable for the manner in which the two large biserial 

 arms of the ray are incorporated in the calyx, coincident with the 

 fixation of pinnules, so as to produce an unprecedented number of 

 pinnule openings directly from the calyx before the arms become 

 free, there being as many as 8 to 12 in some interrays. The number 

 as observed in practice often depends upon the depth to which the 

 arm is broken away in the fossil. 



The species also differs from all others in having the first inter- 

 brachial 10-sided, so that the upper face is angular and supports 

 two large plates in the second range instead of a single one, as is the 

 case normally in all other species of the genus so far as known . These 

 two plates succeeding iBr^ were formerly supposed to be inter- 

 brachials, but with our present understanding of the mode of suc- 

 cession of the incorporated pinnules, it is clear that they are the 

 first pinnulars of the fixed pinnules which lead from the first secundi- 

 brachs, and that this species has actually no interbrachials beyond 

 the first. In the exceptional cases where the iBr^ is truncate, the 



