MARYLAND GEOLOGICAL SURVEY 735 



valve very convex, with a longitudinal ridge and slight lateral depres- 

 sions; beak incurved; umbo prominent." Morton, 1829. 



" Shell large, the dimensions of a large individual being : Length 

 59 mm., width 36 mm., thickness 36 mm. ; elongate oval in outline with sub- 

 parallel sides, often becoming more or les cylindrical in old specimens ; the 

 front margin more or less truncated, sometimes bilobate from a flattening 

 or lobing of the valves anteriorly. Pedicle valve very ventricose, becoming 

 almost gibbous in old individuals, the beak large, strong, incurved, trun- 

 cated at the apex by the large foramen whose diameter is greater externally 

 than within, the truncation in full-grown shells being parallel with the 

 axis of the valves; lateral margins of the beak subangular; the median 

 portion of the valve often flattened or somewhat concave toward the front 

 and the lateral slopes sometimes impressed. Brachial valve much less 

 convex than the pedicle, the beak small and strongly incurved ; the median 

 portion of this valve flattened or concave anteriorly, the flattened portion 

 being bounded on each side by a more or less distinct angular ridge which 

 separates it from, the lateral slope, this feature often being exaggerated 

 to so great an extent as to give the anterior half of the shell a decidedly 

 plicate apearance ; internally the crura are slender near the junction with 

 the valve, and expand rapidly to form a broad loop from 8 mm. to 15 mm. 

 in length, with the width more than two-thirds of the length, the loop 

 sharply angular at the points of recurvature. Surface of both valves 

 marked by numerous lines of growth which are often crowded towards the 

 front of old specimens so as to form distinct varices. Shell substance finely 

 punctate, the punctae usually visible under a hand lens, always more dis- 

 tinctly seen upon exfoliated surfaces. 



" Eemarks. This species is perhaps the largest Terebratuloid shell 

 known in any of the American faunas, and at the horizons where it is 

 found in the Cretaceous formations of New Jersey it usually occurs in 

 great numbers. It usually forms a very constant bed at the summit of the 

 Hornerstown marl where, through several feet of sediments, the shells 

 occur almost to the exclusion of everything else. The species also occurs 

 in the quartz sand facies of the Vincentown formation, sometimes in great 

 numbers, but always in the form of internal casts." Weller, 1907. 



