68 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull.iog. 



era Wyoming, but it differs from that species in having a less promi- 

 inent and rounded umbo; in possessing radiating and concentric 

 wrinkles and radiating raised striae, while that species is an unusually 

 smooth one. In the possession of the radiating raised strise it corre- 

 sponds closely with A. micronema Meek, which is so commonly distrib- 

 uted throughout the Laramie group. As this striation constitutes a 

 more important characteristic than mere form, which is always variable 

 in this genus, it strongly suggests an intimate generic relation for our 

 shell with A. micronema.? 



The specimen now under consideration is slightly more irregular in 

 form and bears rather stronger radiating striae than the type, but the 

 variation is not greater than is often observed in species of this genus. 



At Coalville, Utah, in the same stratum from which the type was 

 obtained, much larger specimens have been found that doubtless be- 

 long to this species. They have the same form of outline, but are less 

 convex. Casts of similar specimens occur in Huerfano park, Colorado, 

 where they are associated with others (described above) that seem to be 

 specifically distinct. 



Locality and position. — The specimen figured is from the Pugnellus 

 sandstone on Muddy creek, Huerfano park, Colorado. The type of the 

 species was found at a higher horizon in the u third ridge " at Coalville, 

 Utah. 



Anomia 1 ? obliqua M. & H. 



Anomia obliqua Meek & Hayden, 1860, Proc. Acad. Nat. Sci., Phila., p. 181. 

 Anomia? obliqua Meek, 1876, U. S. Geol. Sur. Terr., vol. ix, p. 22, PI. 9, Fig. 2. 



This species, which is represented by a single valve, the type, is said 

 to come from the Niobrara division of the Upper Missouri Cretaceous, 

 near the mouth of the Niobrara river. Although the internal charac- 

 ters can not be seen, I am confident that the type is an Ostrea, and 

 probably an immature individual of 0. patina, M. & H. 



Genus PLACUNOPSIS Morris & Lycett. 



Placunopsis? hilliardensis White. 



PI. vni, Fig. 11. 



Placunopsis hilliardensis White, 1879, Ann. Rept. U. S. Geol. Sur. Terr, for 1877, p. 

 278, PI. 7, Fig. 14a. 



Original description: 



u Shell small, broadly oval or subcircular, slightly oblique; test thin, 

 fragile, papyraceous; margins somewhat irregular; upper valve mod- 

 erately convex ; umbo submarginal, the apex depressed and not clearly 

 defined. Surface conspicuously marked with numerous coarse, radiat- 

 ing, irregularly undulating, abruptly raised lines, which are wider than 

 the space between them, and some of which appear to have ended at 

 the border, or upon imbricating concentric lines, as tubular or semi- 



