72 The Upper Cretaceous Deposits of Maryland 



The Monmouth formation presents very simple problems in strati- 

 graphy and structure since the deposits are remarkably homogeneous over 

 extensive areas. ISTo marked change in strike and dip are observable, 

 while no folding of the strata can be detected. No segregation of the 

 formation into members of more than very local extent has been possible. 



Organic Eemains. — The fossils of the Monmouth formation in Mary- 

 land are entirely animal remains of marine type and evidently lived on 

 the continental shelf within the 100-fathom line. The more glauconitic 

 character of the beds and their more homogeneous structure suggest that 

 the habitat of these forms may have been slightly deeper than that of 

 the Matawan fauna, since the conditions of formation of glauconite point 

 to areas of slight deposition of terrigenous materials. The groups of 

 animal remains represented comprise the corals, echinoderms, vermes, 

 bryozoa, Crustacea, pelecypods, gastropods, and cephalopods. The fossils 

 occur chiefly in the dark-colored glauconitic beds, where at a few localities 

 great numbers have been collected in a splendid state of preservation. 



The Monmouth fauna is very much larger than the Matawan, much 

 better preserved and much more cosmopolitan in its affinities. Out of a 

 total of 158 or possibly 164 species listed, 35 per cent are neAV. This high 

 percentage of new forms by no means indicates a local fauna, but rather 

 a very large one which is only imperfectly known. 



There are three areas of distribution in Maryland, one on the Eastern 

 Shore in Cecil County, another along the Sassafras Eiver in Cecil and 

 Kent counties, the third in Prince George's and Anne Arundel counties. 



The Sassafras Eiver fauna though prolific is very poorly preserved, and 

 the determinable species are nqne of them diagnostic of any particular 

 facies. The most striking difference between the Monmouth of Cecil 

 County as developed along the Bohemia Creek and that of Prince George's 

 County is the cephalopod element. The latter is represented on the 

 Eastern Shore by Belemniiella, on the Western Shore by Sphenodiscus 

 lobatus and less commonly by Scaphiles conradi. This suggests an 

 affinity of the former with the Mt. Laurel-Navesink marls, the horizon 

 in which Belemnitella is exceedingly abundant and to which it is 

 restricted. Sphenodiscus, on the other hand, in New Jersey is the most 



