CRETACEOUS ECHINODERMATA. 



Class CBINOIDEA. 



Subclass DICYCLICA. 



Order INADUNATA. 



Suborder DENDEOCRINOIDEA. 



Family PENTACRINID.E. 



Genus PENTACRINUS Blumenbach. 



Pentaceentus tehamaensis Clark, n. sp. 

 Place VI, figure 1. 



Determinative characters. — Column composed of small and medium sized pentagonal joints, 

 some with and some without sharp reentering angles. Crenulated ridges petaloid. Column 

 perforated by a small canal. 



Dimensions. — Column: Diameter of joint 3 to 6 millimeters; thickness of joint \ to 1 

 millimeter. 



Description. — Numerous isolated fragments of Pentacrinus columns have been found in 

 the California Cretaceous. The larger joints are of medium size. Many very small joints are 

 found with the larger ones and probably belong to the same species. The crenulations are dis- 

 tinct and form five well-marked petaloid areas on the upper and lower surfaces of the joints. 

 The column is perforated by a small central canal. 



Localities. — Shelton's ranch, 5 miles north of Paskenta, Tehama County (type), and Texas 

 Springs, Cal. 



Geologic horizon. — Knoxville formation, Lower Cretaceous, and beds doubtfully assigned to 

 the lower part of the Chico formation, Upper Cretaceous. 



Collection. — U. S. National Museum (31194). 



Pentacrintjs beyani Gabb. 



Plate VI, figures 2a-b. 



Pentacrinus bryaniGabb, 1876, Acad. Nat. Sci. Philadelphia, Proc, vol. 28, p. 178, PI. V, figs. 1, la, lb. 

 Pentacrinus bryani Clark, 1893, Johns Hopkins Univ. Circ, vol. 12, No. 103, p. 51. 

 Pentacrinus bryani Clark, 1893, U. S. Geol. Survey Bull. 97, pp. 28, 29, PI. Ill, figs. 3a-b. 

 Pentacrinus bryani Johnson, 1905, Acad. Nat. Sci. Philadelphia Proc, vol. 57, p. 6. 



Pentacrinus bryani Weller, 1907, Cretaceous paleontology of New Jersey: Geol. Survey New Jersey, pp. 276-277, PL VI, 

 figs. 8, 9. 



Determinative characters. — 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 of medium size. 



Dimensions. — Column: Diameter of joint 6 millimeters; thickness of joint 1 rnillhneter. 



Description. — Two small fragments of the stem of this form were described by Gabb in 1876. 

 As the first representative of this family reported from the American Cretaceous it possesses 

 considerable interest. The column is composed of moderately large, thick joints, that reach 

 about 6 millimeters in diameter and about one-fifth of that in thickness. The broad, rounded 

 ridges at the salient angles of the pentagonal outline form a nearly unbroken hue, and £he furrow 

 at the reentering angles is alternately depressed and elevated in successive joints. The edge 



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