stanton.] TRIGONIID.E, UNIONJDJE, SOLEMYID.E. 95 



TRIGONIID^E. 



Genus TRIGCXNTA Bruguiere. 



Trigonia ? 



Trigonia Meek, 1873, Ann. Rept. U. S. Geol. Sur. Terr, for 1872, pp. 474. 475. 



A few imperfect specimens of a Trigonia allied to T. evansana Meek 

 have been collected at Cinnabar mountain and near Gallatin city, Mon- 

 tana. The specific characters are not sufficiently well preserved to 

 be described. It is remarkable that these are the only specimens of 

 Trigonia reported from the Upper Cretaceous of the north interior 

 region. The genus is well represented in the beds of the same age in 

 the Atlantic aud Gulf border regions from New Jersey to Texas, and 

 also on the Pacific coast. 



UNIONID^E. 



Genus UNIO Eetzius. 



Unio ! 



i 

 PI. xxii, Fig. 1. 



Fragments of TJnio are not uncommon, associated with the coal beds 

 near the base of the Colorado formation in southern Utah. One of the 

 best preserved specimens obtained at Glendale, Utah, is figured. This 

 form, which is abundantly represented there by fragments and casts, 

 seems to be distinct from all the described Cretaceous species, though 

 the material in hand is hardly sufficient to characterize it. It is a rather 

 slender, compressed form, its outline broadly lanceolate. The beaks, 

 which are not very prominent, are situated one-third to one-fourth the 

 length of the shell from the anterior end. The cardinal and basal mar- 

 gins are subparallcl, the anterior end regularly rounded, and the poste- 

 rior end more narrowly rounded or subtruncate. The surface is smooth, 

 excepting the posterior third, which is marked by two obscure radiating 

 folds or plications. Length of the figured specimen, 66 mm ; height, 26 mm . 

 Some of the fragments belonged to shells nearly twice as large as this. 



SOLEMYID^E. 



Genus SOLEMYA Lamarck. 



SOLEMYA? OBSCURA U. Sp. 



PI. xxi, Fig. 8. 



Shell small, thin, elongate, subcylindrical; ventral and dorsal mar- 

 gins nearly parallel ; anterior? end regularly rounded; posterior'? end 

 contracted immediately behind the beak, rather narrowly rounded; 

 beak broad, incurved, not very prominent, situated near the posterior? 



