22 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



Locality. — Two and one-half miles west of Round Mountain, Shasta County (type), and at 

 Rush Creek, Plumas County, Cal. 



Geologic horizon. — "Cedar formation," Upper Triassic. 



Collections. — U. S. National Museum (31185); Leland Stanford Junior University. 



ISOCEINUS sp. 



Pentacrinus asteriscus (?) Hall and Whitfield, 1877, IT. S. Geol. Expl. 40th Par. Final Rept. vol. 4, pp. 230, 281, PL VI, 

 fig. 16. 



Hall and Whitfield examined several column joints of supposed Pentacrinus collected by 

 Arnold Hague of the 40th Parallel Survey "in limestone of supposed Triassic age, associated 

 with Spiriferina Tiomfrayi and Terebratula Jiumboldtensis Gabb, near Dun Glen Pass, Pahute 

 Range, Nevada," which they doubtfully referred to P. asteriscus Meek and Hayden of the Juras- 

 sic of the Rocky Mountain region. They note certain differences "in the more obtuse points of 

 the star, and the filling up of the angles between the points, and also in the broader form of the 

 elliptical figures on the articulating surfaces of the disks." They state that although these fea- 

 tures are not constant the form is larger than P. asteriscus, and that better material would doubt- 

 less show it to be another species. It is evident that this form can not be safely referred to the 

 Jurassic species P. asteriscus, but as the author has not had access to further material it is simply 

 referred to the genus Isocrinus without specific description. The limestones at Dun Glen Pass 

 were correlated with the base of the Star Peak formation, and more recent work has confirmed 

 this determination. * The Star Peak formation is of both Middle and Upper Triassic age. 



Locality. — Dun Glen Pass, Pahute Range, Nevada. 



Geologic horizon. — Limestone of Dun Glen Pass, Middle Triassic. 



Collection. — U. S. National Museum. 



Family ENCRINID.E. 



Genus ENCRINTJS C. F. Schulze. 



Encrintjs hyatti Clark, n. sp. 



Plate I, figures 3a-b. 



Determinative characters. — Column composed of large, thin, round to oval joints. Surfaces 

 of joints covered with fine, bifurcating striations, producing a close suture. Column perforated 

 with canal of rather smaU size. 



Dimensions. — Column: Diameter of joint 5 to 10 millimeters; length of joint 1 to 3 milli- 

 meters. 



Description. — Several specimens of casts of the column joints of Encrinus have been exam- 

 ined by the author from a single Upper Triassic locality in California. The column itself is 

 wanting in every specimen, but the cast of the "close surface" is very perfect, much more so than 

 the cast of the outer surface, which in all specimens has lost its distinctive features. Most of the 

 casts show a somewhat oval outline, which may be due to compression, as the stems of most of 

 the species belonging to this genus are round. 



The joints surpass considerably in size those of any other crinoid form in the American 

 Mesozoic. The round to oval shape of the "close surface" of the specimens and the fine bifur- 

 cating striations thereon are highly distinctive, enabling the relations of the form to be readily 

 determined even in small fragments. All the specimens evidently belong to the same species. 

 A rather small canal is present. 



Locality. — Oscar tunnel, 2\ miles southeast of Longville, Plumas County, Cal. 



Geologic horizon. — "Cedar formation," Upper Triassic. 

 Collection. — U. S. National Museum (31186). 



i During the progress of this report through the press a paper by J. P. Smith (The Middle Triassic marine invertebrate faunas of North 

 America: U. S. Geol. Survey Prof. Paper 83, 1914) has appeared, in which he says (p. 148): "A species identical with that of Dun Glen, Nev., 

 occurs iu the Pit shale of California, associated with a poor fauna characteristic of the Middle Triassic." It is referred to Pentacrinus cf. 

 P. asteriscus Meek and Hayden. 



