THE LOWER EMBAR OF WYOMING 657 



depth of water, most species are widely distributed. As most of 

 them are not bottom dwellers, their remains are about as likely 

 to be found in one kind of rock as in another. The time range 

 of most species is small. Of 112 species of cochliodont sharks 

 listed by Hay in his Bibliography and Catalogue of Fossil Vertebrates, 

 only three have a vertical range of more than one formation and 

 the identifications in the three cases are not always reliable. The 

 wide distribution, independence of bottom conditions, and small 

 vertical range make them of particular value in correlating strata. 

 But unfortunately most fossil fishes are labeled, as the older collec- 

 tions of invertebrates were, as from a given locality and formation, 

 without more specific data. 



The writer has been at work for several years in trying to 

 assemble the data on fossil fishes for use in correlation. 



INVERTEBRATES FROM THE LOWER EMBAR 



Orbiculoidea utahensis Meek (PL III, Figs. 22-25) 



1877. Discina sp. undet. Meek, U.S. Geol. Expl. 40th Par., Rept., IV, 99, 



PL 10, Fig. 3. 

 1877. Discina utahensis Meek, ibid., IV, 99. 



1910. Lingulidiscina utahensis Girty, U.S. Geol. Surv., Bull. 436, pp. 24-25. 

 PL I, Fig. 11. 



191 1. Lingulidiscina utahensis Woodruff, U.S. Geol. Surv., Bull. 452, p. 13. 

 191 1. Lingulidiscina utahensis Blackwelder, U.S. Geol. Surv., Bull. 470, 



P- 477- 

 1913. Lingulidiscina utahensis Blackwelder, Am. Jour. Sci., 4th Ser. ; 

 XXXVI, 178. 



Much of the lowest phosphate bed is a sort of coquina made 

 up, for the most part, of pedicle valves of this species. The average 

 diameter of the shells is a little more than 2 cm. I have followed 

 Girty in identifying this species as 0. utahensis, but comparison 

 with specimens from the Coal Measures of Missouri, identified as 

 Orbiculoidea convexa Shumard, shows no differences of specific 

 value. The brachial valve figured in PI. Ill proves that the 

 species is not a Lingulidiscina. 



Plagioglypta canna White (PL III, Fig. 13) 

 This species is common and seems to be the only one that 

 ranges from the lowest phosphate bed through the higher beds. 



