Maryland Geological Suiniiv 561 



Length 37 iniii.; width 55 mm. 



Occurrence. — Jexnixgs Formation, Ciikmlnu ^Ilmbkr. MillstDiie, 

 2444. 



Collect ion. — ]\IiirvliUH] Geological Survey. 



Family PRODUCTIDAE 



Genus CHONETES Fischer 

 ChONETES LEPIDIFORMIS 11. sp. 



Plate L, Figs. 6-10 



Description. — Clionetes Icpidus Hall, a common si)eeies occurring in 

 the Hamilton fauna of New York, and extending into tl'c taui^a of the 

 Ithaca and Chemung beds, is a shell cliaractei'ized hy its small size and 

 2 strong divergent median plications, between which lie 3 or 4 small 

 plications. On the lateral slopes are 10-13 shar^) angular plications 

 which bifurcate freely (see Paleontology of Xew York, vol. iv, p. 132, pi. 

 xxi, fig. 5, pi. xxii, figs. 12, 13). This character of surface is ])resented by 

 a Maryland shell which deviates from ('. lejiidiis in its larger size, pro- 

 portions and the degree of its plication. At tiuic'^ approaching that 

 species very closely, these shells show a variability in form and surface 

 which recjuires for them a distinct designation thiuigli tlicy show in 

 their own structure their ancestry as is suggested in the specific name. 



Shells small or of medium size for this genus; generally subsemi- 

 circular or slightly elongate axially, often however quite transverse. Sur- 

 face depressed convex. Two strong striae or plications start at the beak, 

 soon taking on the character of low folds dividing into plications Init 

 leaving a marked axial depression between them to tlie pallial margin. 

 In some cases 2 plications of conspicuous size are continuous from beak 

 to margin and in this respect the resemblance to C. lepidus is pro- 

 nounced. The axial plications are somewhat smaller than the rest and 

 each of the lateral slopes may bear 12-15 plications which bifurcate 

 toward the margin. The cardinal margin of the ventral valve bears 

 spines of considerable length the outermost being directed outward with 

 a slight curve. The shells of this species attain a length of 10-12 mm. 

 and usually have aliout the same width on the hinge. 

 36 



