1896.] "'^'^ [Smith. 



tian county, 8 N., 33 W., section 13, shows the perfect resemblance 

 between the two so-called species. There are live distinct but rather 

 rounded plications on each side of the mesial fold and sinus, but no 

 concentric striations or lamellae were observed. The entire surface is 

 thickly covered with short spines, which seem to be unusually well 

 preserved. 



This species was found in the Lower Coal Measures of Conway county, 

 6 N., 16 W., section 39, southwest quarter of southwest quarter, and in 

 the Upper Coal Measures at the locality mentioned in Sebastian county; 

 also on Poteau mountain, Indian Territory ; in the Lower Carbonifer- 

 ous, Boone Chert, upper Burlington or lower Keokuk, at St. Joe, in 

 Searcy county. 



Subkingdom Mollusca. 



Class Lamellibran cMata. 



Genus Aviculopecten, McCoy. Aviculopecten curhoniferus Stevens, 

 Amer. Journ. Sc, Vol. xxv, p. 361. 



Two imperfect specimens from the Lower Coal Measures, White 

 county, 8 N., 7 W., section 36, southeast quarter, agree fairly well with 

 the figures and descriptions of this species. Another specimen was 

 found in the Lower Coal Measures of Conway county, 5 N., 16 W., sec- 

 tion 17, northwest quarter. 



Aviculopecten coxanus Meek and Worthen, Proc. Aaid. Ndt. Sc. Phil., 

 1860, p. 453 ; Geol. Surv. Ill, ii, p. 336, PL xxvi. Fig. 6 ; F. B. Meek, 

 U. S. Geol. Surv. Nelrasica, p. 196, PL ix. Fig. 3. 



This species is found in the Upper Coal Measures of Illinois and Ne- 

 braska, and was also found in the same horizon on Poteau mountain,. 

 Indian Territory. 



Aviculopecten germanus Miller and Faber, Journ. Cin. Soc. Nat. Hist.,. 

 July, 1893, p. 79. 



This species was described from the Coal Measures of Elkhorn creek„ 

 Kentucky, and was compared by tlie authors to A. rectilaterarius Cox 

 sp., Geol Surv. Kentucky, iii, p. 571, PI. ix. Fig. 3, but it resembles; 

 more closely A. eclwardsi "Worthen, Bull. 2 State Mus. Nat. Hist, of 111., 

 p. 33 ; both species were founded on left valves, the right being un- 

 known. They are both very similar to A. segregatus McCoy, British 

 Pal. Fossils, p. 489, PI. iii, E, Fig. 1, of the Carboniferous limestone of 

 Northumberland, although the latter has from two to three secondarv 

 intermediate ribs, instead of one. 



A single small left valve was found in the Upper Coal Measures of 

 Poteau mountain, Indian Territory. It agrees in the main points with 

 Miller and Faber's description, except that the intermediate rib is some- 

 times obsolete, and distinct concentric lines of growth are seen on the 

 shell. 



