40 MESOZOIC AND CEN0Z0IC ECHINODEKMATA OF THE UNITED STATES. 



the circumference line; the transverse articular ridge process is reduced to two elongated tubercles which proceed from 

 the marginal rim. Central canal comparatively large. 



Although this species is still very imperfectly known one can affirm that it is certainly distinct from Bourgueticrinus 

 ellipticus Miller, by the much less swollen form of the basal cone, which is but slightly convex in outline, and by the 

 facts that the lower segment of the cone is already elliptical and already possesses the rudiments of a transverse articular 

 ridge. Furthermore, the radiating carinas are very much more salient, and consequently the depressions which they 

 separate very much deeper. Finally, by its central canal being relatively much larger. 



This species is referred to the genus Rhizocrinus, following the views of Carpenter and also 

 from the possible close relationship of the form to Rhizocrinus cylindricus Weller from New Jersey. 

 Locality. — Livingstone, Ala. (De Loriol). 

 Geologic horizon. — Ripley formation, Upper Cretaceous. 

 Collection. — Cincinnati Society of Natural History. 



Rhizocrinus cylindricus Weller. 



Plate VII, figures 5a-g. 



Rhizocrinus cylindricus Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 275, 276, 

 PI. VI, fig. 1. 



Determinative characters. — Weller says: 



Calyx cylindrical, slender and greatly elongate, the sides almost straight, not enlarging from the basals up. The 

 proximal colunm joint (or joints ?) higher than the basals and radials together, cylindrical above with straight sides, 

 slightly contracted below. Basals much higher than the radials. Radial facets shallow, curved, rather wide, separate, 

 low and not sloping upward, having no conspicuous muscle plate or ligament fossa. They inclose a relatively large and 

 well-excavated central funnel or visceral cavity. 



Dimensions. — Height of proximal column joint and calyx together 9.3 millimeters; diameter 

 3 millimeters; height of proximal column joint 6 millimeters. Isolated joints: width 2 to 4 

 millimeters; height 3 to 3.5 millimeters. 



Description. — This species is established on a single complete calyx and proximal stem 

 joint, although numerous isolated column joints may belong to the same species. Several of 

 these column joints were collected a number of years ago by the author. Figures of some of the 

 more characteristic ones were first given by Weller from drawings furnished by the author and 

 are repeated here. 



Related forms. — The specimen is clearly a member of the family Bourgueticrinidae and 

 superficially resembles in some respects Bourgueticrinus ellipticus and B. sequalis from the White 

 Chalk of England, but it differs from these species iu the much greater height of its basals. The 

 character of the radial facets and the larger viceral cavity, however, seem to remove it from 

 that genus. In the great height of its basals the species agrees with members of the genus 

 Rhizocrinus, but that genus is described as having a thin, disklike proximal stem joint, whereas 

 the New Jersey species apparently has an exceedingly high one in which no transverse divisions 

 can be detected. There seems to be no reason, however, why some latitude may not be allowed 

 in this character. The genus Rhizocrinus has not heretofore been recognized earlier than the 

 Eocene, but there is no reason why it should not also occur in the later Cretaceous. 



The species is possibly allied to Rhizocrinus alabamensis (De Loriol) but diffe-s from that 

 species in having a much more slender form. 



Locality. — Vincentown, N. J. 



Geologic horizon. — Yincentown sand of the Rancocas group, Upper Cretaceous. 



Collection. — New Jersey Geological Survey; Johns Hopkins University. 



