Maryland Geological Survey 253 



concentric lines of growth are conspicuous and have a somewhat im- 

 bricating appearance in addition to which are fine concentric striae; the 

 lines of growth and striae are very much crowded on the ear, which is 

 perhaps a little larger than on the figured specimens of this species. The 

 proportion of leng-th and height of this specimen is apparently more equal 

 than for the normal forms of the species, although perhaps the greater 

 height is partly due to crushing. 



Length and height, about 37 mm. 



Occurrence. — Komney Formation, Hamilton Member. West of 

 iron bridge over Town Creek northeast of Oldtown. 



Collection. — Maryland Geological Survey. 



LlOPTERIA laevis Hall 

 Plate XXIX, Fig. G 



Leiopteria laevis Hall, 1883, Nat. Hist. New York, Paleontology, vol. v, pt. i, 



Lamellibr. (adv. copy), pi. xvii, figs. 5-11. 

 Leiopteria laevis Hall, 1884, Nat. Hist. New York, Paleontology, vol. v, pt. i, 



Lamellibr. 1, p. 158, pi. xvii, figs. 5-11; pi. xx, fig. 5. 

 Leiopteria laevis Hall, 1884, Thirty-fifth Rep. New York State Mus. Nat. 



Hist., p. 334. 

 Leiopteria laevis Cleland, 1903, Bull. U. S. Geol. Surv., No. 206, p. 67. 

 Leiopteria laevis Kindle, 1912, Bull. U. S. Geol. Surv., No. 508, p. 95, pi. viii, 



fig. 5. 



Description. — This species is represented in the collection by a single 

 left valve. Hall ' described tlie species as follows : " Shell small, sub- 

 rhomboidal ; body obliquely ovate ; length and height nearly equal ; 

 greatest length below the middle; margins regularly roitnded, somewhat 

 extended on the post-basal side. Left valve more convex than the right ; 

 the greatest convexity in both valves is above the middle. Hinge-line 

 straight on the posterior side of the beak, turning abruptly down in 

 front; entire length greater than the length of the shell. Beaks obtuse, 

 rounded, inclined forward, situated at the anterior third of the shell, 

 that of the left valve quite prominent. TJmbonal region of left valve 

 prominent, subtending an acute angle. Ear triangular, nearly equi- 



'■ Pal. New York, vol. v, pt. i: i, 1884, pp. 158-159, pi. 17, figs. 5-11; pi. 20, fig. 5. 



