MapxYlaxd Geological Survey 649 



Occ-Hrrc^ce.— Jennings Formation, Paukhead Member. Williams 

 Koad, on Polish Mountain, 1289. 



( 'olh'ciion. — Maryland (Jcological Surve}'. 



AVICULOPECTEN ? Sp. 



Description. — An imperfect valve which has heen observed in the 

 Chemung at Allegany Grove is probably referable to this genus. It has 

 not been figured. 



Occurrence. — Jennings Formation, Chemung Member. Allegany 

 Grove, 1633. 



Collection. — jMaryland Geological Survey. 



Genus LYRIOPECTEN Hall 



Lyriopecten tricostatus (Yanuxem) 



Plate LXV, Fig. 1 



Avicula tricostata Vanuxem, 1842, Geol. of N. Y., Rept. 3d Dist., p. 179, fig. 1. 

 Lyriopecten tricostatus Hall, 1884, Pal. of N. Y., vol. v, pt. i, p. 48, pi. iv, 

 fig. 11; pi. vii, fig. 26; pi. x, figs. 6-12. 



Description. — Shell large, subcircular or obliquely broad-ovate; beak 

 subcentral. Wings relatively small and smooth. Surface marked by 

 strong simple and distant radial costge most of which reach the umbo, 

 those of the major series being 14-lG in number. These are abruptly 

 elevated from the general surface and in the broad flat interspaces are 

 finer stride usually of two orders, the larger in the middle and the lesser 

 at the sides. 



This is a very well-characterized species of the New York Chemung 

 fauna. Few examples have been observed in the Maryland rocks. 



Length 45 mm. ; height 45 mm. 



Occurrence. — Jennings Formation, Chemung Member. Oakland- 

 Altamont Eoad; Oakland-Eedhouse Eoad; National Road 6 miles west of 

 Frostburg; 2 miles west of Pawpaw, West Virginia; on county road near 

 top of Jennings, top of Green Eidge. 



Collection. — Maryland Geological Survey. 



