68 The Upper Cretaceous Deposits of Maryland 



The Matawan is represented in Maryland and Delaware in two distinct 

 areas, the one along the Chesapeake and Delaware Canal, Delaware, and 

 the other in Anne Arundel County, Maryland. 



The fauna of the Delaware area is much less homogeneous in char- 

 acter than that of Maryland, and some of the faunal zones which Weller 

 differentiated in New Jersey apparently persist to the southwest, though 

 much less sharply defined than at the type localities. In general, the 

 fauna becomes increasingly younger to the eastward. The presence of 

 Exogyra costata near Delaware City and of Belemnitella at Briar Point 

 indicates that there is probably some Monmouth from the canal dump 

 mingled with the Matawan at these localities. In the immediate vicinity of 

 Summit Bridge and at Post 105 a fauna is represented analogous to that 

 of the Merchantville and Woodbury of New Jersey. Among the most 

 characteristic species in the fauna of approximately twenty species are 

 Anchura rostrata, Turritella delmar, Laxispira lumbricalis, Liopistha 

 altemata, Mortoniceras delawarensis, Placenticeras placenta, and Sca- 

 phites hippocrepis. Turritella delmar, which is one of the most abundant 

 species, was described from Delaware and has been reported only from 

 the environs of the type locality. Laxispira lumbricalis, Anchura 

 rostrata, Placenticeras placenta, and Scaphites hippocrepis are character- 

 istic Merchantville forms, while Mortoniceras delatvarensis and Liopistha 

 altemata are peculiar not only to the Merchantville but to the Mortoni- 

 ceras subzone of the entire eastern United States and Gulf. Because of 

 the presence of this characteristic genus the horizon has been called by the 

 name of the Mortoniceras subzone rather than the more local term " Mer- 

 chantville." Furthermore, the Summit Bridge fauna is probably the 

 equivalent not of the Merchantville alone but of both the Merchantville 

 and the Woodbury. Even within the limits of New Jersey Weller noticed 

 that the differentiation between them became increasingly difficult toward 

 the south, and in Delaware it is apparently obliterated. Both typical 

 Merchantville forms, such as Mortoniceras delatvarensis, and typical 

 Woodbury forms such as Yoldia longifrons, occur at a single locality, 

 although the earlier types are dominant. 



