462 Systematic Paleontology 



Occurrence. — Helderberg Formation, Iveyser Member. Keyser, 

 West Virginia. 



Collection. — U. S. National Museum. 



[Maynard.] 



Section DYSODONTA 

 Superfamily MYTILACEA 

 Family MODIOLOPSIDAE 



Genus MEGAMBONIA Hall 



Megambonia lamellosa Hall 

 Plate LXXVIII, Fig. 5 



Megam'bonia lamellosa Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 467, pi. cix, 

 figs. 5, 6, 1861. 



Description. — " Shell obliquely ovoid, very gibbous in the middle and 

 towards the umbo ; the body of the shell rather abruptly narrowed above 

 the middle. Anterior wing short, rounded, very convex, separated from 

 the body of the shell by a broad rounded depression, leaving a sinus in the 

 margin. Posterior wing broad triangular, extending more than two-thirds 

 the entire length of the posterior slope ; its junction with the body of the 

 shell marked by a depression. Surface marked by concentric lamellose 

 striae, wiiich, on some parts of the specimens, are very prominent. Faint 

 remains of radiating striaj are somei:imes perceptible on the casts." Hall, 

 1859. 



It has been found only in the form of casts, but is not uncommon in the 

 Oriskany of Maryland. 



Length about 3.5 cm. ; height 2.5 cm. 



Occiirrence. — Oriskany Formation, Ridgely Member. Queen's 

 Point opposite Iveyser, Miller's Spring, and Knobly ]\Iountain, West 

 Virginia; near Cumberland, Hancock, Maryland. 



Collections. — Maryland Geological Survey, IT. S. National Museum. 



[Ohern.] 



