650 Systematic Paleoxtology — Uppek Devoxiax 



Superfomily MYTILACEA 

 Family MODIOLOPSIDAE 



Genus MODIOMORPHA Hall 

 MODIOMORPHA SDBANGULATA Hall 



Plate LXV, Fig. 2 



Modiornorpha suhangulata Hall, 1885, Pal. of N. Y., vol. v, pt. i, sec. ii, p. ^87, 

 pi. XXXV, figs. 10, 11. 



Description. — ■"' bliell of medium size, elongate subovate, wider behind ; 

 length more than twice the height, basal margin slightly arcuate, abruptly 

 rounding at the extremities ; posterior margin acutely, rounded below and 

 obliquely subtruncate to the cardinal line; cardinal margin nearly 

 straight. Anterior end rapidly declining from the beak and abruptly 

 rounded below. Valves moderately convex in the posterior part, and gib- 

 bous and subangular in the umbonal region. There is a broad depression 

 or sinus which extends from just posterior to the beak to the basal margin 

 near the middle of the length of the shell. Hinge-line slightly oblique, 

 extending about half the length of the shell. Beaks almost anterior, 

 prominent, small, angular, incurved and elevated above the hinge-line. 

 Umbonal region gibbous, with a prominent ridge extending from the 

 beaks to the postbasal extremity, angular in its upper portion, becoming 

 more subdued toward the posterior end. Test thick, marked by fine eon- 

 centric striae, which are sometimes fasciculate, making stronger ridges 

 on the surface. Anterior end marked by a strong, muscular impression 

 just below the beak, close to the anterior margin. A large individual of 

 this species has a length of 55 mm.; and a height of 26 mm. A smaller 

 specimen has a length of 39 mm., ,and a height of 19 mm. This species 

 bears some resemblance to M. suhalaia, but differs in its much stronger 

 and more angular umbonal ridge, which reaches to the postbasal ex- 

 tremity, the basal margin is more arcuate, the cardinal and basal margins 

 are more nearly parallel, and the anterior end is shorter." Hall, 1885. 



Occurrence. — Jennings Formation, Chemung Member. Williams 

 Koad, on Polish Mountain, 2382. 



Collection. — Maryland Geological Survey. 



