Maryland Geological Survey 637 



Occurrence. — Jennings Formation, Chemung Member. Two miles 

 south of Oakland, Garrett County. 



Collection. — ^Maryland Geological Survey. 



Leptodesha longispinum Hall 



Plate LXIII, Figs. 4-8 



Avicula longispina Hall, 1843, Geol. Surv. N. Y., 4th Dist., p. 2G2, fig. .". 

 Leptodesma longispinum Hall, 1884, Pal. of N. Y., vol. v, pt. 1, p. 179, pi. xxi, 

 figs. 14, 17-19, pi. Ixxxix, figs. 2-4. 



Description. — Shell rather small, elongate subrhomboidal, body elon- 

 gate, obliquely ovate, length gi'eater than height; margin from byssal 

 sinus to beyond the base broadly rounded, posterior margin regidarly 

 recurved. Posterior wing prominent, depressed on right valve and on 

 both produced into a long narrow spine. Surface convex on both valves 

 broadly depressed by the anterior oblique sinus, this depression dis- 

 tinguishing the species from forms like L. lichas having similar pro- 

 portions but with a broader anterior ventral slope. Fine regular con- 

 centric lines over all the surface. 



Dimensions of an average specimen; length from anterior to posterior 

 extremity 25 mm. ; height complete 1-i mm. 



This species is quite common in the sandy flags at various localities 

 seldom however attaining the size which it frequently reaches in the 

 Chemung fauna of New York. 



Occurrence. — Jennings Formation, Chemung Member. Near Deer 

 Park; National Eoad 6 miles west of Frostburg; Ellerslie, Pennsylvania, 

 1508. 



Collection.' — Maryland Geological Survey. 



Leptodesma agassizi Hall 

 Plate LXIII, Figs. 9, 10 



Leptodesma agassizi Hall, 1884, Pal. of N. Y., vol. v, pt. i, p. 182, pi. Ixxxix, 

 figs. 17-19. 



Description. — Shell of medium size, subrhomboidal ; body broadly 

 ovate and more erect than in associated species of the genus. Anterior 



