580 Systematic Paleontology — UrPER Devoxiax 



Caviaiodichia eximia Hall and Clarke, 1S93, Pal. of N. Y., vol. viii, pt. ii. 

 p. 192, pi. Ivii, figs. 44-45. 



Description. — Shell triiuigulai'-ovatc. length and -width siibequal. 

 valves subequally convex. Angle over nmbo acute. Ventral valve moder- 

 ately convex at innbo; a wide undefined sinns arising near middle of 

 valve and becoming pliglitly better defined near front. Dorsal valve about 

 as convex as vential valve; a fold beginning near middle of valve which 

 is sometimes distinct, but is usually illy defined. Surface bearing from 

 l-t to 28 plications of which 4, 5 or at times G are in sinus and a corres- 

 ponding number on fold. A mesial septum is present in the ventral 

 valve, extending to near middle of valve. 



Length usually 7 to 12 mm. ; width alxnit the same. 

 The shells referred to C. cximid differ from the larger individuals 

 figured by Hall in tl-.e Paleontology of Xew York, vol. iv, and resemble 

 the younger specimens illustrated by him. They are characterized by 

 possessing fine plications, finer than in the other sjiecies of the fauna, 

 illy defined sinus and fold, and in being usually slightly cunvex. This 

 species is frequent in the Parkhcad and al)undant in the up}ier part of 

 the Chemung. Specimens occurring in the upper iron-rich strata are 

 usually small and apparently depauperate. 



Occurrence. — Jennings Formation, Chemung Mejibeu. Allegany 

 Grove, 2020, 29G0: Town Creek, 3870, 3937, 3942 common, 3963 abund- 

 dant, 3982, -±031, 471U; 2 miles west of Pawpaw, West Virginia, 384G, 

 4570, 4G3G, 4G94 common. Parkhead Member. Two and one-fourth 

 miles southeast of Cumberhmd. on road 1 mile north of JJockv Pun and 

 1% miles east of Kuobly ^rouutaiii ; Williams l.'oad, on Polish ^fountain, 

 1289, 1352, 1371; 2 miles north of mouth of Town Creek, 1312; Sideling 

 Hill Creek 2i/i miles above mouth; Woodmont, 1285; Hancock. KiOO; 

 Millstone, IGOO. Individuals with unusually deep sinus occur abundantly 

 in the Chemung at Town Creek 39G3 and 2 miles west of Pawpaw, West 

 A'irginia. 384G. 



VolJectioii. — Marvland Geological Survev. 



