508 GEOLOGICAL SUEVEY OF THE TERRITOEIES. 



Physa Gaeletoni, Meek. 



Shell rhombic-siibovate, attaiuing a medium size; very tbin; spire 

 short and small; volutions about three, last one very large, or forming 

 near nine-tenths the entire bulk of the shell; aperture unknown ; sur- 

 face showing rather obscure lines of growth. 

 ' Length, 0.56 inch; breadth, 0.35 inch. 



The only specimen of this species I have seen is somewhat imperfect, 

 .and so connected with a portion of the arenaceous matrix that its 

 aperture and columella cannot be seen. It seems to hav^e most nearly 

 resembled such recent species as P. Lordi, Baird, in general form. I 

 should not have attempted to name and characterize the species without 

 seeing the columella and aperture, had it not seemed desirable to call 

 attention to it as the first species of the genus hitherto found in the 

 well-marked Cretaceous strata of this country. 



The specific name is given in honor of Mr. Benjamin Carleton, the 

 gentleman who owns the coal-mine at which the specimen was found, 

 and assisted us in collecting the fossils found at the same. 



Locality cmd position. — Carleton's coal-mine, near Coalville, Utah, in a 

 Cretaceous bed, associated with Unio, Cardiiim, I?ioceramus, Anoinia, 

 Neritina, and other marine and fresh- water shells. 



Species from the Bitter Creek series. 

 OsTEEA Wyomingensis, Meek. 



Osirea Idriaensis ? ? Meek, 1872. Haycleu's Geological Report, Montana, «fec., p. 375, 



(not O. Idriaensis, Gabb.) 



Osirea Wyomivgensis, Meek, 1872; lb. 



Shell attaining a moderately large size, rather compressed, subovate, 

 or trigonal-subovate, being pointed at the beaks, and more or less 

 rounded at the opposite extremity. Lower valve usually rather shallow ; 

 beak generally somewhat acutely pointed, undistorted, and nearly al- 

 w^ays curved upward at the extremity; ligament area comparatively 

 small, trigonal, with the longitudinal furrow and transverse strise well 

 defined ; i^osterior lateral margins flattened, and rather broad, in conse- 

 quence of the lateral expansion of the imbricating laminse of growth: 

 muscular scar comparatively small ; surface with only irregular imbri- 

 cating but not strongly projecting laminae of growth. Upper valve 

 smaller than the other, nearly flat on the upper side and slightly con- 

 cave within ; beak less pointed than in the other valve, being usually a 

 little truncated at the extremity, which is straight or nearly so ; liga- 

 ment area of the same size and nearly the same form as in the other 

 valve, excepting that it is not curved, but directed obliquely uj^ward 

 and backward, and has its anterior margin forming a transverse ridge, 

 as usual most prominent in the middle at the end of the mesial longi- 

 tudinal ridge, which is rounded, or somewhat flattened, and continued 

 to the point of the beak; posterior lateral margins thickened in adult 

 shells, and only rarely showing slight traces of crenulations; surface as 

 in the other valve. 



Length of large examples from beak to anterior extremity, 6 inches ; 

 breadth, 4 inches. Average-sized specimens are generally a little nar- 

 rower in proportion to length. 



In Dr. Hayden's report of 1872, I referred this oyster witli much 

 doubt to 0. Idriaensis, Gabb ; but at the same time expressed the opin- 

 ion that it would probably prove to be a distinct and undescribed species, 



