L'.)-) 



moulds. Hinge area very narrow, with the cardinal margins concave. Dental 

 lamellae prominent, placed at right angles to one another. 



Dorsal valve flat or very slightly concave, represented by only a single frag- 

 mentary specimen, preserving the interior processes in too imperfect a condi- 

 tion for description. 



On each valve there are about 14 to IG low, rounded, often obscure, radiating 

 plications, of medium size, generally broader than the reverse plications, 

 though frequently equaling them in width. They are smaller, and sometimes 

 more distinct near the beak, than at the front, the cardinal angles and the sides 

 being always smooth for a greater or less width, while the front is frecjuently 

 nearly smooth. 



One ventral valve measures as follows: Length, 14 m. m., breadth, 21 

 m. m., height, about 3 m. m. ; another, 14 m. m., 18 m. m., and about 8 m. m. 



It is impossible to separate the specimens of Trojn'dolejjtus of 

 Erere, from those forms of Trojjidoleptus carinatus of New York, 

 wliieh are not carinate along the median line. 



Obtained with ;S'. Pedroana, etc., from the Devonian sandstone 

 of Erere, where it is moderately abnndant. (Morgan Expedition 

 1871.) 



Vitiilina pustulosa, Hull, Piute IX, figs. 2, G-S, 11-18, 15, 20, 21, 27 and 82. 



Vitulinapustulosa, Hall, 13th Rep. St. Cab. N. Y., 18G0, p. 82. 

 VitnUnaivistulosa, Hall, Pal. N. Y., Vol. IV, p. 410. 



The test of the Erere forms is of moderate size, with the ventral valve very 

 convex, and the dorsal valve flat or very slightly convex ; transverse, the 

 breadth varying from one and one-fourth to one and one-half times the length, 

 and greatest at or just anterior to the hinge line, which last is straight. Cardi- 

 nal extremities usually subangular in young specimens, but becoming rounded 

 in the larger and full grown ones. Lateral and anterior margins forming to- 

 gether a very broad, semi-elliptical curve, which is slightly flattened along the 

 front of the test. 



Ventral valve most prominent at or just posterior to the middle, and fur- 

 nished with a median fold, more or less elevated above the surface of the 

 valve, and formed of two, rounded, prominent i)lications, each of which is 

 very small where it commences at the beak, and increases rather rapidly in 

 size towards the front. The plications are separated by a rounded or slightly 

 flattened, and generally well defined reverse plication, and each slopes more or 

 less abruptly on the outer side, to a still larger reversed plication, beyond 

 which the sides of the valve slope to the lateral margins with little or no 

 curvature, generally making the valve somewliat broadly subcarinate along 

 the median line. The fold increases very gradually in height from the beak, 

 and the curve along its top is generally quite strong, sometimes becoming 



