PART I CHAZYAN AND RELATED BRACHIOPODS—COOPER 753 
Same horizon in Vermont: Just north of neck of Providence Island, Lake 
Champlain, Plattsburg (15’) Quadrangle. 
Discussion.—This species is a fairly early member of the genus as it occurs 
in the Crown Point formation of the Chazy group. It is flatly convex, is lamel- 
lose like most other species and has fairly fine ornamentation. It is also charac- 
terized by a large visceral area which does not strongly overhang the geniculated 
trail. This species differs from all others herein described, except L. platys and 
L. occidentalis, in its low convexity. It is a larger and deeper shell than L. occi- 
dentalis but is somewhat less convex and larger than L. platys and is differently 
ornamented. 
LEPTELLINA PULCHRA Cooper, new species 
Plate 189, A, figures 1-23; plate 195, C, figures 9-16; plate 219, G, figure 14 
Shell large for the genus, strongly concavo-convex, wider than long. Cardinal 
extremities obtuse, auriculate. Lateral margins well rounded; anterior margin 
broadly rounded. Surface marked by 8 to Io narrow, elevated threadlike cos- 
tellae that stand out over a field of very fine costellae, about 5 in 1 mm. The 
fine costellae are of very even grade. In addition to the costellae, 2 specimens 
show evidence of fine concentric lamellae like those of Sowerbyites. In some 
specimens a few oblique wrinkles are present along the posterior margin on each 
side of the beak. 
Pedicle valve with posterior third somewhat flattened but strongly convex in 
the anterior two-thirds in lateral profile; anterior profile a narrowly rounded 
arch. Beak small, protruding slightly beyond the posterior margin. Umbonal 
region slightly swollen; swelling continued forward in the median part of the 
valve to the front margin to form a fold. Lateral slopes slightly convex, steep. 
Anterior slope steep. Interarea slightly apsacline. 
Brachial valve deeply concave with the greatest concavity just anterior to the 
middle; umbo concave, the concavity continued anteriorly as a poorly defined 
sulcus ; flanks gently concave and regions parallel to posterior margin also con- 
cave. Cardinal extremities concave. 
Interior: Muscle area of pedicle valve wide and short, equal in length to about 
one-quarter the length of the valve; dental plates short and stout; adjustor- 
diductor patches set off from the adductor field by low ridges in old shells; 
pallial sinuses not strongly impressed. Brachial valve with well-developed, large 
visceral area, the front margins of which are produced forward and overhang 
the geniculated front slope; median ridge slender, high, not extending to the 
chamber under the cardinal process. Brachial processes slender and flat. Cardi- 
nal process a slender ridge bounded by 2 triangular depressions, the whole 
grown together with the chilidial plates to form a single plate, which in this 
species, is undercut and overhangs an umbonal chamber somewhat like the cardi- 
nalia of Sowerbyella. Area of muscle attachment thickened and marked by 
oblique ridges. 
