358 DR WHEELTON HIND ON THE LAMELLIBRANCH AND 



APPENDIX. 



Since completing and presenting my account of the lamellibranch fauna in the 

 Millstone Grit in Scotland, the following specimens have been collected by the officers 

 of the Geological Survey from the cores of the Plean Bore near Stirling. 



Edmondia nebrascencis, Geinitz, sp., 1866. (PI. II. fig. 34.) 



Astarte nebrascencis, Geinitz, 1866, Garb, unci Dyas in Nebraska, p. 16, Tab. i. fig. 25. 

 Edmondial ,. Meek, 1872, Fin. Rep. U.S. Geo!. Surv. Nebraska, p. 214, pi. x. fig. 8, a, b. 



Miller, 1889, N. Amer. Geol. and Pal., p. 479. 



Specific Characters. — Shell slightly transverse, subovate, only moderately gibbose, 

 unequilateral. The anterior end is short, its margin regularly rounded. The inferior 

 margin is broadly curved. The posterior border is bluntly rounded. The hinge line 

 is slightly arcuate. The umbones are small, slightly elevated, placed at the junction 

 of the anterior and middle thirds of the hino-e li ne< 



Interior. — Not yet examined. 



Exterior. — The surface is ornamented by concentric, fine, raised, fairly equidistant 



. linear ridges which separate moderately wide concentric sulci which are finely linear 



transversely. This marking is more characteristic in the new parts of the valve, 



towards the inferior margin ; in the umbonal or juvenile part of the shell the lines 



and grooves are crowded. Under the microscope very fine radiating lines are seen. 



Dimensions. — A right valve from Nebraska in my collection measures : antero- 

 posteriorly, 22 mm. ; dorso-ventrally, 17 mm. 



Locality. — Stirlingshire, Sheet 24 N.W., Eosehill diamond bore, \\ mile E. of 

 Plean. 



Observations. — Some half-dozen specimens of this species have been obtained from 

 the diamond bore at Eosehill. E. nebrascensis is very closely related to E. M'Coyii, 

 Hind, but it has some slight differences in the ornament. The concentric lines are more 

 sharply linear and finer, especially in the older part of the shell, and in one specimen 

 I made out the radiating markings mentioned by Meek in his species. In general 

 shape there is no real difference between the species, and they are very closely allied, 

 but E. M^Coyii is the more gibbose of the two. I have a series of fine specimens from 

 Nebraska, and have been able to compare these with the Scotch examples and the series 

 of shells which served me for the study of my species E. M l Coijii. Unfortunately the 

 Scotch examples are very badly preserved ; but specimens T£|£f£?, PI. II. fig. 34, show 

 the characteristic marking of the valve. The series from Eosehill show a greater tendency 

 to variation of the ornament in the older and younger portions of the shell than my 

 American series. Sanguinolites occidentals occurs in the Shale with E. nebrascensis. 



