MAEYLAND GEOLOGICAL SURVEY 641 



margin feebly excavated ; anterior lateral margin rounding obliquely into 

 the base; posterior very short and squarely truncate; base line smoothly 

 convex in the anterior and medial portion, rapidly ascending and very 

 feebly concave behind the median vertical ; external sculpture very feeble, 

 little more, indeed, than irregular incremental striations; character of 

 hinge and interior not known. 



Dimensions. Altitude 4.75 mm., latitude 6.75 mm., diameter, 4 mm. 



It is separated from Cuspidaria cucurbita n. sp. by its smaller size and 

 less produced and less evenly inflated anterior end. The type is unique. 



Occurrence. MONMOUTH FORMATION. Brightseat, Prince George's 

 County. 



Collection. Maryland Geological Survey. 



CUSPIDARIA CUCURBITA n. sp. 

 Plate XXXVII, Figs. 4, 5 



Description. Shell of moderate size for the genus, oblique, minutely 

 gourd-shaped; subequivalved, the right valve a little the more inflated; 

 umbones gibbous, incurved, the apices proximate and opisthogyrate, placed 

 a little behind the median horizontal; anterior dorsal margin gently 

 sloping ; lateral margin obscurely truncate ; posterior portion of shell 

 abruptly contracted and compressed, behind the umbones ; posterior dorsal 

 margin feebly excavated, the short lateral margin squarely truncate ; base 

 line arcuate in the anterior and medial portion, rapidly ascending pos- 

 teriorly; characters of surface and interior not known. 



Dimensions. Altitude 7 mm., latitude 10.5 mm., maximum diameter 

 of double valves 6 mm. 



The cast of the double valves from which the shell is described suggests 

 in its outline a miniature drinking gourd, the evenly inflated anterior and 

 medial portion forming the cup, the abruptly constricted posterior por- 

 tion the neck. The species is probably a close relative of Cuspidaria ven- 

 tricosa Meek and Hayden, but it is much more oblique than the latter, and 

 differs further in that the base line is not excavated at the rostrum. From 

 Cuspidaria ampulla n. sp. it is separated not only by the larger size but 



