41li CARBONIFEROUS FORMATTONS AND FAUNAS OF COLORADO. 



Locality and horizon. — San fluaii region (.station 2;22()); upper portion of the 

 Hermosa formation. Loadville district (station ^^04); base, of the Weber formation. 



AvicuLOPECTEN ? INTERLINEATUS Mceic and Worthen. 

 PI. VIII, fig. 3. 



1860. Aviculopeeten interlineatus. Meek and Worthen, Acad. Nat. Sci. Philadelphia, Proc, p. 454. 



Upper Coal Measures: Lasalle, 111. 

 1866. Ar!culopecten interlineatus. Meek and Worthen, Geol. Surv. Illinois, Kept., vol. 2, p. 329, pi. 26, 

 fig. 7a, b. 



Upper Coal Measures: Lasalle, 111. 

 1877. Aviculopedcnf interlineatus. White, U. S. Geog. Geol. Surv. AV. 100th Mer., Rept., vol. 4, p. 149, 

 pi. 11, fig. 3a. 



Carboniferous: Confluence of White Mountain and Black rivers, Arizona. 

 1884. Arkidopecten(f) inlcrlineatux. White, Geol. Surv. Indiana, 13th Kept., p. 145, pi. 30, fig. 9. 



Coal Measures: Indiana{?). 

 1891. Aviculopeeten interlineatus. Whitfield, New York Acad. Sci., Ann., vol. 5, p. 604, pi. 16, figs. 10, 11. 



Coal Measures: Hocking Count}-, Ohio. 



1894. Aviculopeeten? interlineatua. Keyes, Missouri Geol. Surv., vol. 5, p. 112, pi. 42, fig. 6. 

 Upper Coal Measures: Kansas City, Mo. 



1895. Aviculopeeten interlineatus. Whitfield, Geol. Surv. Ohio, Rept., vol. 7, p. 489, pi. 12, figs. 10, 11. 

 Coal Measures: Falls Township, Hocking County, Ohio. 



1900. AvictUopecten interlineatus. Beede, Univ. Geol. Surv. Kansas, Rept., vol. 6, p. 116, pi. 13, fig. 6. 

 Upper Coal Measures: Kansas City, Kansas. 



This well-marked species is represented by but two specimens, as usual each 

 from a different localit3^ Both valves are present, one of which (the left) is shown 

 by fig. 3 on PI. VIII. Each of the broad concentric bands is terminated below by a 

 thin, high ridge vertical to the surface, and there are a number of intermediate ridges 

 which are considerably smaller and le.ss prominent. 



The right valve has much the shape of the right valve of A. occidemtalis. It differs 

 from the left in having the anterior ear narrower and bounded below by a deep sinus. 

 The surface is marked hj broad concentric bands and delicate sublamellose striae, but 

 seems to lack the elevated ridges by which the opposite valve is characterized. The 

 strise are more or less wavy and irregular. There are also indications of very faint, 

 irregular, intei'mittent, radiating ribs which, though visible without a glass, can 

 only be seen in a favorable light. 



While the shape of the right valve of this species is very like the corresponding 

 one of A. occidentalis, the difference in surface characters is such that, when once 

 noted, there is little danger of mistaking one for the other. 



Locality and horizon. — Crested Butte district (station 2293); Maroon formation. 



