28 THE MESOZOlO EICHINODEHMATA OP UNITED STATES. !fi«Lt.07. 



formed from outward aspect (PI, lii, Pig. 4(0. A distinctly petaloid 

 arraDgement of the creimlated ridges is exhibited (PL in, Pigs. 4a, 4fe). 



Hall and Whitfield refer to Pentacnnites asterisetis Meek and Hayden 

 certain specimens collected by Hague in Nevada from " limestone of 

 supposed Triassic age." There is some doubt as to the identity of this 

 form, though the description and figures render it probable that it 

 should be referred to F. Whitei. 



The form figured and described ^by Whitiield from the Black Hills 

 under the name P. aster iscus is, on account of the deep reentering angles, 

 to be probably associated with P. Whitei. No side view of the joints is 

 given by which comparison may be made. 



Related forms. — Separated from P. asteriscus, with which it has been 

 hitherto confounded, by its larger size, deeper reentering angles, and 

 relatively much thinner plates. 



Locality and geological horizon. — The type specimens of this form are 

 from the Jurassic of Salt creek and Diamond valley, Utah. 



Collection. — U. S. National Museum. 



Pentacrinus Bryani Gabb. 

 Plate III, Figs. 3a-h. 



Pentacrinus Bryani Gabb, 1876. Philadelphia Acad. Nat. Sci. Proc, vol. 28, p. 178, 

 PI. 5, Figs. 1, Irt, U. 



Determinative characters. — Calyx wanting. Column composed of 

 moderately large, rather thick, pentagonal joints, with sharp reentering 

 angles. The crenulated ridges are broadly petaloid and each area is 

 rounded at its outer extremity. Column perforated by canal. 



Dimensions. — Column: breadth of joint, ./o.iuch; length of joint, 

 ^ inch. 



Description. — Two small fragments of the stem of this form are 

 described by Gabb iu the Proceedings of the Academy of Natural 

 Sciences of Pliiladelphia for 1870. As the only representative of this 

 family reported from the American Cretaceous it possesses considera- 

 ble interest. The column is composed of moderately large, thick joints, 

 that in breadth reach quite one-quarter of an inch iu diameter and 

 about one-fifth of that in thickness. The broad rcmnded ridges at the 

 salient angles of the i)entagonal outline form a nearly unbroken line, 

 while the furrow at the reentering angles is alternately depressed and 

 elevated in successive joints. The edge of each joint is slightly rounded. 

 The crenulated surfaces form five broad petaloid areas distinctly 

 rounded at the outer extremities (PI, in. Fig. 3(() and' unite near the 

 inner edge of the reentering angles to form a double fiat-topped ridge 

 that reaches to the central canal, around which there is likewise a 

 slight elevation. The crenulations are visible on the outer surface of 

 the column. The column is i^erforated by a central canal. 



Belated forms. — As the only representative of this family in the 



