624 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



of the Great Oolite, Pt. II, p. 75, PL VII, fig. 8, seems to be a closely 

 related form. 



It occurs at east end of northeast spur from Signal Peak; saddle in 

 ridffe west of south branch of head of Gardiner; head of Fawn Creek 

 northeast of Monument Peak and Cinnabar Mountain. Specimens collected 

 by Dr. Peale at Devils Slide, Cinnabar Mountain, were labeled and listed 

 by Meek 1 as "Cucullsea." 



Pholadomya kingi Meek. 

 PI. LXXIV, figs. 1-3. 



Pholadomya kingi Meek, 1873: Ann. Kept. U. S. Geol. Surv. Terr, for 1872, p. 473. 

 White, 1S80: Idem for 1878, p. 150, PI. XXXVIII. tigs, a and b. 



This abundant species varies considerably in sculpture, and the fact 

 that almost every specimen in the collection is distorted in various ways by 

 pressure causes it to appear much more variable in both form and sculpture 

 than it really is. 



The type specimen figured by White, which is itself somewhat distorted, 

 has eleven radiating costse on the central region of the valve, though they 

 are not quite so prominent as they are represented in the drawing above 

 referred to. Most of the specimens from the Park have fewer (usually not 

 more than eight or nine) costas, and on flattened specimens these are some- 

 times barely visible. 



Pholadomya nevadaua Gabb, from the Lias of Volcano, Nevada, is evi- 

 dently a related species, and Professor Hyatt- has treated P. kingi as a syno- 

 nym of it. Compared with Gabb's figure and description, however, P. kingi 

 is smaller and more slender and has the beaks farther from the anterior end. 

 The costse also are differently arranged. Professor Hyatt has compared 

 for me specimens of the Yellowstone form with those from California 

 referred to P. nevadana, and he is now inclined to regard them as distinct. 

 It is at least safer to keep them separate until direct comparison can be 

 made with Gabb's type, which seems to be lost, or with specimens from the 

 original locality. 



The species occur in the collection from divide between Fawn Creek 

 and Gallatin Valley; east end of northeast spur from Signal Peak; saddle 



1 Anu. Rept. U. S. Geol. S-rv. Terr, for 1872, p. 474. - Bill. Geol. Soc. Am., Vol. V, p. 418. 



