FOSSIL CRINOIDS. 145 



men; and I have now two good specimens of the same species from the typical 

 locality, Tournai, showing the anal side, in which the anal x, while rising high 

 between the first brachials, is also well down between the radials, and rests 

 directly upon the posterior basal. I have figured them both, and there is no 

 doubt about this (PI. V, figs. 4, 5). The plate is in the same condition as shown 

 in the diagram and figures of Hall's type of S. simplex (Geol. Iowa, II, 549, 

 PL 9, fig. 10). These specimens are from the Mountain Limestone of Belgium, 

 about equivalent to our Lower BurHngton. Now it is significant that in the 

 latter formation there is a species in which, among a number of well preserved 

 specimens, the anal x varies in position from between the radials, resting on the 

 truncate posterior basal, to nearly beyond them, resting only on their corners, 

 as in de Koninck's figure. On such a specimen Meek and Worthen described 

 their Erisocrinus antiquus, which, with the other Burlington species described 

 by them, must go out of Erisocrinus. In all these, as well as in the other species, 

 including S. simplex from the Upper Burlington, the top of the anal plate rises 

 high above the level of the distal face of the radials. There cannot be the 

 slightest doubt that they all fall under Graphiocrinus, and for this reason Hall's 

 name Scaphiocrinus must be discarded as a synonym. 



It is evident that Trautschold's Phialocrinus and Miller and Gurley's Aesio- 

 crinus are also merely synonyms of Graphiocrinus; substantially the same type 

 of anal structure, accompanied by similar unbranched arms, 10 or less in number, 

 with quadrangular brachials, runs under these names successively through the 

 Kinderhook, Burlington, Keokuk, St. Louis, and Kaskaskia, to the Upper Coal 

 Measures. The extreme ventral sac of the Upper Carboniferous form, upon 

 which Aesiocrinus was founded, is only an exaggeration of the sac existing in the 

 Kinderhook species, and in the same horizon is found a small species, G. (Sca- 

 phiocrinus) carbonarius Meek and Worthen, very similar to the latter. It is nota- 

 ble also that in both the Burlington and Upper Coal Measure forms there is a 

 tendency to reduction in the number of arms, from 10 to 9, 7 and 5. The type 

 is a simple and generalized one as to its calyx elements, and therefore long lived. 



The situation thus resulting necessitates a name for the species heretofore 

 ranked under Scaphiocrinus. Fortunately this can be provided without pro- 

 posing a new one, simply by reviving the genus Pachylocrinus, proposed by 

 Wachsmuth and Springer in 1879 (Rev. Pa!., I, 11")), and afterwards abandoned 

 by us in Part III, 242, where we, without good reason, referred its species to 

 Woodocrinus. The genus was not very clearlj' defined to start with, but there 

 was a fairly definite assemblage of species, and, what is more important, a 



