SYSTEMATIC REVISION OF SPECIES. 

 SELACHII. 



Genus JANASSA Miinster. 

 Beitr. Petrefakt., 1832, p. 67, 

 Revised description of genus: 



1. Depressed, ray-like sharks belonging to the extinct family 



Petalodontidce. 



2. Teeth in each jaw arranged in a pavement composed of several 



rows; those in median row the largest, and those in the lateral 

 rows gradually diminishing in size. 



3. Each tooth a flattened plate reflexed at both ends so as to appear 



j^shaped in lateral view; the proximal reflexed part the root. 

 Middle portion of tooth traversed on inner surface by a series 

 of fine ridges. 



Carboniferous and Permian Periods. Represented in the Permian of 

 America by two species, Janassa strigilina and /. gurleyana. 



Janassa strigilina (Cope). (Plate 26, figs. \-ih.) 



1878. Strigilina linguaformis Cope, Proc. Amer. Philos. Soc, xvii, p. 52. 



1881. Janassa strigilina (Cope), Amer. Nat., p. 163. 



1887. Janassa strigilina (Cope), Trans. Amer. Philos. Soc, xvi, p. 285. 



1889. Janassa strigilina (Cope), Woodward, Cat. Fos, Fishes, i, p. 38. 



1900. Janassa strigilina (Cope), Case, Journ. GeoL, viii, p. 699, pi. I, figs. la-lc. 



Type: A tooth, probably belonging to a median series. Gurley Col- 

 lection, No. 6500 University of Chicago. Vermilion County, Illinois. 



Original description of species: "The plicate surface terminates behind 

 in a median angle, at the base of the root. There are eight plicae which all 

 cross the plane, excepting the sixth, which is interrupted in the middle by 

 the strong angulation of the seventh, which touches the fifth. The lateral 

 extremities of the right are in contact with the base of the recurved cutting 

 portion. The latter is convex transversely, leaving a smooth surface between 

 it and the eighth plica. The smooth side of the tooth is shining, and there 

 is a shallow fold, which passes around its side and crosses just at the base of 

 the recurved cutting lamina. 



"Measurements. m 



"Total length of the plane 0.008 



Width at base of the cutting lamina * .006 



Width at the base of the root 004 



Thickness of plane portion 0015" 



Janassa gurleyana (Cope). (Plate 26, figs. 2-2i.) 



1878. Strigilina gurleiana (Cope), Proc. Amer. Philos. Soc, xvii, p. 191. 



1881. Janassa gurleiana (Cope), Amer. Nat., xv, p. 163. 



1889. Janassa gurleiana (Cope), Woodward, Cat. Fos. Fishes, i, p. 39. 



1900. Janassa gurleyana (Cope), Case, Journ. Geol., viii, p. 700, pi. i, figs. 2a-2c. 



Type: A small tooth lacking the root. Gurley Collection, No. 6501 

 University of Chicago. Vermilion County, Illinois. 

 156 



