150 FOSSIL CRINOIDS. 



of their Fig. 3c, PI. VIII, which, however, it resembles but little. But Miller's 

 species is better characterized by the loose plates he figures; and it is probable 

 that the Austin's P. plicatus (Mon., 78, PI. IX, fig. 4a) is the same thing. Their 

 P. radiatus (Men., PI. X, figs. la, b) is almost indistinguishable in the calyx 

 from my younger specimens figured as P. doris, but the arms and ventral sac 

 are so different as to make one wish to see the original specimen before making 

 comparisons; they look much more like those of Parisocrinus. P. spissus 

 de Koninck and Lehon has nothing in the known parts to distinguish it from 

 Miller's P. tenuis. 



The genus Poleriocrinus has a wide distribution, occurring in the Eifel, 

 Belgium, Britain, and America. It ranges from the Devonian to culmination 

 at the end of the crinoidal formation composed of the Burlington and Keokuk 

 Limestones. It may be represented in the St. Louis by a small species described 

 by Meek and Worthen as P. hurdianus (Geol. Surv. 111., V, 533); the figure 

 is incorrect as to the anal side, and the specimen itself not very clear. The 

 Devonian species described by Schultze, P. cuiius and P. stellaris (syn. P. 

 angulosus) , are strongly typical of the genus, and Schultze himself remarked 

 the extraordinary resemblance of some of them to British Carboniferous species. 

 The ventral sac, as shown in P. curtus, (Mon. Echin. Eifelk., PI. V, figs. 4a, h), 

 is constructed exactly on the plan of that of Poteriocrinus as now understood, 

 and not of Parisocrinus, to which it was referred in Revision of the Palaeocrin- 

 oidea, I, 115; the arm shown in the figure is recuperated, and may not have 

 the normal number of brachials. From the calyx alone it is not easy to dis- 

 tinguish between a low form of Poteriocrinus and Vasocrinus, though I think 

 the radianal, as a rule, is larger in the former; with either the ventral sac or 

 arms preserved the distinction would be clear. 



Of the thirteen species ranged under the typical form of the genus by Wach- 

 smuth and Springer, Rev., I, 111, two, never figured, P. obuncus White, and P. 

 whitei Hall, should be removed, both having wide facets. While adding a re- 

 markable new species to the list, I will first give some much needed illustrations 

 of two other important species, hitherto unfigured. 



