MARYLAND GEOLOGICAL SURVEY 349 



bonal slope, by being less produced posteriorly and by having a much 

 less concave posterior dorsal margin. The yoimg of the two species 

 are qnite distinct and need never be confused with each other. 



This species seems to be confined to the lower of the two fossiliferons 

 beds at Governor Run, Jones Wharf and that horizon elsewhere, and 

 characterizes it just as the C. marylandicus seems confined to, and is 

 characteristic of, the upper of these fossilifarous beds. 



Length, 87 mm.; height, 55 mm.; diameter, 17 mm. 



Occurrence. — Choptank Formation. Governor Eun (lower bed), 2 

 miles south of Governor Run (lower bed). Flag Pond (lower bed). Jones 

 Wharf, Pawpaw Point, Cuckold Creek, Greensboro. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum, Philadelphia Academy of Natural Sciences. 



Crassatellites UNDULATUs (Say). 



Crassatella undulata Say, 1824, Jour. Acad. Nat. Sci. Phila., voL iv, 1st ser., p. 142, 



pL xii, tig. 2. 

 Crassatella undulata Conrad, 1832, Fossil Shells of tlie Tertiary, p. 28, pi. ix. 

 Crassatellites (Scambrtla) undulatus var. cijclopterus Dall, 190.3, Trans. Wagner Free 



Inst. Sci., vol. iii, pt. vi, p. 1474. 



Description. — This species is believed to be another of the Virginia 

 forms given to Say by Finch and erroneously described as coming from 

 Maryland. No authentic Maryland specimens of this species are known 

 by the writer. 



Occurrence. — " Maryland " (Dall) . 



Subgenus CRASSINELLA Guppy. 



Crassatellites (Crassinella) duplinianus Dall. 



Plate XCIV, Fig. 13. 



Crassatellites {Crassinella) duplinianus Dall, 1908, Trans. Wagner Free Inst. Sci., vol. 

 iii, pt. vi, p. 1478, pi. 1, tigs. 5, 6. 



Description.—'' Shell small, subtriangular, solid, with markedly acute 

 beaks, which incline backward : anterior slope convexly arcuate, long; 

 posterior slope nearly a straight or slightly concave line, shorter; lunula 

 and escutcheon extending the whole length of their respective slopes, 

 long and narrow, the latter more excavated than the former and wider; 



