Maryland Geological Survey 263 



tending from tlie beaks and producing a constriction or sinuosity in the 

 basal margin. Test thick, marked by lamellose concentric lines of growth, 

 without other ornamentation. The hinge is characterized by numerous 

 small teeth or callosities beneath the beak, which appear to be without 

 special arrangement, the posterior ones being directed backward and some- 

 times more elongated ; lateral teeth two or three in number, parallel and 

 extending nearly to the post-cardinal extremity; anterior muscular im- 

 pression deep and strong; specimens vary in length from 21 to 52 mm. 

 and in height from 11 to 24^ mm. 



An imperfect internal impression of a left valve was obtained at 

 McCoys Ferry Avhich is with some hesitation referred to this species. 

 It has a similar outline and proportions with prominent arcuate, um- 

 bonal ridge and conspicuous parallel lateral teeth; but there is a con- 

 spicuous and fairly deep furrow extending from slightly in front of the 

 beak obliquely across the anterior part of the shell which is fai'ther 

 forward and more prominent than the oblique constriction crossing N. 

 arguta. The furrow of this specimen is perhaps partly due to crushing. 

 Later, additional specimens were obtained at other localities. 



Length, 39 mm.; height, 19 -{- mm. 



Occurrence. — Eomney Formation, Hamilton Member. McCoys 

 Ferry; southwest of McCoys Ferry; on east side Warrior Mt. east of Kush. 



Collection. — Maryland Geological Survey. 



Superfamily PECTINACEA 



Family PECTINIDAE 

 Genus AVICULOPECTEN McCoy* 



AvicuLOPECTEN PRiNCEPS (Conrad) 

 Plate XXXI, Figs. 10, 11 ; Plate XXXII, Figs. 1, 2 



Monotis princeps Conrad, 1838, An. Rop. N. Y. GeoL Surv., p. 117. 

 Avicula parilis Conrad, 1842, Proc. Acad. Nat. Sci. Phila., voL viii, p. 239, pi. 

 cxii, fig. 9. 



' Dr. G. H. Girty has recently stated that the spelling Aviculipecten is the 

 etymologically correct one (Amer. Geol., vol. xxxlii, 1894, p. 295). 



