Cincinnatiafi and Lexington Fossils 27 



represented by the interval. In the case of Orthorhynchiila linneyi^ 

 a larger number of the Fairmount specimens have a more globose 

 form, due to a less angular junction of the valves along the lateral 

 margin, but more globose and more angular forms may be noticed 

 at both horizons. The normal number of plications on the fold is 

 four, but in the specimens from the Greendale division of the 

 Cynthiana formation, at Pleasant Valley, the number is increased 

 not infrequently, by intercalation, to five or six. 



The muscular scar of the pedicel valve has a quadrate appear- 

 ance due the parallel lateral outlines produced by the internal thick- 

 ening of the shell on each side. It is of fairly large size. In a 

 specimen having a length of 22 mm., the muscular scar had a width 

 of 8 mm. and a length of 1 1 mm. The interior outline of the scar 

 usually is moderately convex but may be nearly straight. 



Rhynchotrema dentata — arnheimensis. 



(Plate III, fig. 13.) 



Rhynchotrema dcntata-arnhcimcnsis was found loose at the 

 Arnheim horizon, a quarter of a mile east of Andersonville, and in 

 situ at the same horizon half a mile south of Arnheim, and a mile 

 and a half south of Russellville; all in Brown county, Ohio. In 

 Kentucky, it occurs three miles south of Maysville; also at the 

 Brown's run school house, two miles northeast of Rectorville and 

 8 miles southeast of Maysville; at the foot of the hill east of 

 Wyoming, 30 miles south of Maysville; about a third of a mile 

 southwest of Sunset, on the road to Day's mill; half a mile south- 

 west of Howard mill, on the road over the hill to Spencer; a mile 

 south of Indian Fields, and then two miles west, at the Curry 

 bridge across Howard creek; four miles north of Richmond, at the 

 railroad cut north of Ophelia ; a mile north of Rowland, on the 

 west side of Logan creek; near the Pleasant Valley church, south- 

 west of Rush Branch post office; three miles southeast of Lebanon, 

 a mile south of the home of P. L. Mudd, along a branch entering 

 Caney creek from the east; a mile west of Lebanon, northwest of 

 the home of Col. J- B. Wathen; half a mile north High Grove; 

 a mile south of Smithville ; near the home of J. D. Stansbury, a mile 

 and a half south of Mount Washington ; four miles southeast of 

 Jeffersontown, where the road descends abruptly toward Floyd 

 creek, a mile east of Shinks branch ; three quarters of a mile west 



