DESCEIPTIOlSrS OF SPECIES. 343 



aria figured by Meek as L. mytiloides, and L. tighti Herrick. But the study of 



these forms is most difficult and but little profitable. 



Locality and hmnzon. — Leadville district (station 2264?); base of the Weber 



formation. 



LiNGULA TIGHTI Herrick. 



1887. lAngula tighti. Herrick, Sci. Lab. Denison Univ., Bull., vol. 2, p. 43, pi. 4, fig. 5 

 Coal Measures: Flint Ridge, Ohio. 



This species is found at but one locality. It is there very abundant, though not 

 well preserved. The material studied is as a rule much smaller than L. carhonaria, 

 which has been identified at another locality in the Leadville area, but the essential 

 difference resides in the fact that it is a more slender and elongate form, with a shape 

 which is rather subelliptical than subquadrate. Most of the material referred to 

 this species is also smaller than the specimen figured b}' Herrick, but one or two 

 examples from the same locality and apparently belonging to the same specific type 

 are nearly of normal size. It i.s possible, however, that we have here only young 

 shells of Z. carhonaria. 



This species is very abundant in the Lingida bed of station 2227. One peculi- 

 arity of the occurrence at this locality is that in most instances both yalves are 

 found in conjunction. 



In addition to the material belonging to the genus Lingida, whose specific iden- 

 tification has been attempted as above, several occurrences of indeterminable speci- 

 mens may be noted, e. g. , Glenwood Springs, station 2193a. 



Locality and horizon. — Leadville district (station 2277); base of the Weber for- 

 mation. 



ORBICULOIDEA d'Orbigny, 1850. 



Orbiculoidea manhattanensis Meek and Hayden. 



1859. Discinn manhattanensis. Meek and Hayden, Acad. Nat. Sci. Philadelphia, Proc, p. 25. 



Upper Coal Measures: Kansas River, opposite Manhattan, Kans. 

 1892. Orbiculoidea manhattanensis. Hall and Clarke, Int. Study of Brach., pt. 1, pi. 5, fig. 12. 



Coal Measures: Riley County, Kans. 

 1892. Orbiculoidea manhattanensis. Hall and Clarke, Pal. New York, vol. 8, pt. 1, pi. 4E, fig. 20. 



Coal Measures: Riley County, Kans. 

 1900. Orbiculoidea manhattanensis. Beede, Univ. Geol. Surv. Kansas, Rept., vol. 6, p. 56, pi. 8, figs. 

 2-2b. 

 Upper Coal Measures: Wabaunsee formation, black shale in wagon-road cut east side of Blue 



Mount, Manhattan, Kans. 

 Of this .species but few specimens have come to hand, and they are crushed and 

 fragmentary. The best preserved example, a dorsal valve, affords the following 

 data: 



The shape is of course nearly circular, with a diameter of about 15 millimeters. 



