MESOZOIC FOSSILS. 617 



Flat Mountain. It was originally described from Wind River Valley, 

 Wyoming, and it also occurs in the Black Hills. The type is Meek's 

 figured specimen, No. 1893, United States National Museum collection. 



PSEUDOMONOTIS CURTA (Hall)? 



Avicula (?) custa Hall, 1852: Stansbury's Kept. Gt. Salt Lake Exp., p. 412, PL IV, 



figs, la, b. 

 Eumicrotls curta (Hall) Meek and Haydeu, 1865: Paheont. Upper Missouri, p. SI, 



PI. Ill, figs. Wa^d. 

 Pseudomonotis (Eumicrotis) curta (Hall) Whitfield, 1880: Geol. Black Hills Dakota, 



p. 351, PI. Ill, figs. 20-25. 



A single imperfect specimen from summit of ridge between Red and 

 Basin creeks is doubtfully referred to this species. The hinge and umbonal 

 region are wanting, and the identification is based simply on general form 

 and surface sculpture of the fragment. The species is abundant in the 

 Jurassic of the Black Hills. The original spelling of the specific name 

 custa seems to have been a typographical error that was corrected by Meek, 

 and the form curta has since been followed. 



GERVILLIA MONTANAENSIS Meek. 



Gervillia montanaensis Meek, 1873: Ann. Eept. U. S. Geol. Surv. Terr, for 1872, p. 472. 

 White, 1880: Idem for 1878, p. 145, PI. XXXVII, figs. 1« aud b. 



Distinguished by its large size and its long posterior wing. The 

 types are from near the lower canyon of the Yellowstone, and it has been 

 collected on divide between Fawn Creek and Gallatin Valley; east side of 

 Fan Creek Pass; Cinnabar Mountain, and summit of ridge between Red and 

 Basin creeks, near Sheridan Peak. 



Gervillia sp. 



A smaller and much more slender species of Gervillia is represented 



by fragments from east end of northeast spur from Signal Peak, stream bed 



west of Quadrant, jr., and saddle in ridge west of south head of Gardiner 



River. 



Mopiola suBiMBRiCATA Meek. 



Modiola (Vulsella) sitbimbricata Meek, 1873: Arm. Rept. IT. S. Geol. Surv. Terr, for 



1872, p. 472. 

 Volsella subimbricata White, 18S0: Idem for 1878, p. 145, PI. XXXVII, figs. 2«-c. 



This species seems to be widespread, but not very abundant at any 



