THE KIMMSWICK AND PLATTIN LIMESTONES 
201 
11. Rhynchotrema rowleyi sp. nov. 
Plate XXIII, fig. 2 A-D 
Shells of large size, occurring as separated valves with the 
anterior margin more or less broken off. In the three best pre- 
served pedicel valves, with lateral diameters of 28, 29, and 33 
mm., the lengths are estimated at 27, 29, and 33 mm., and the 
convexities at 8, 8, and 9.5 mm. respectively. Three plications 
occupy the sinus of the pedicel valve, and five or six plications 
occupy each side, leaving an unplicated space 5 or 6 mm. wide 
between the last plication and the postero-lateral angle of the 
valve. Four plications occupy the median fold of the brachial 
valve, and four occur on each side, occasionally with a trace of 
a fifth lateral plication. The plications are crossed at regular 
intervals by conspicuous and rather coarse concentric striae, of 
which five or six occur in a length of 5 mm. on the more central 
parts of the valves and toward the beak. In addition to the 
coarser striae, some valves show much finer concentric striae, 
and the latter tend to dominate along the unplicated postero- 
lateral parts of the valves and also along the anterior, more or 
less gerontic part of the valves. 
The interior of both valves is constructed as in Rhynchotrema 
capax, but the muscle scars are more deeply impressed. Ad- 
ductor scars impressed in the posterior part of the muscular 
area, distinctly defined laterally, 3 mm. wide and almost 6mm. 
long. The remainder of the muscular area is occupied by the 
diductor scars which are crossed by more or less irregular radi- 
ating lines. The posterior part of the diductor scars embraces 
the adductor scars. The area occupied by the diductor scars is 
deeply impressed postero-laterally and is fairly distinct even an- 
teriorly; its width is II mm., and its length is 12 or 13 mm. The 
pitted ovarian markings occupy the area between the deeply 
impressed postero-lateral parts of the diductor scars and the 
nearest lateral margins of the shell. The teeth project upward 
and inward, and posterior to the teeth are distinct sockets for 
articulation with the posterior part of the hinge plates on the 
brachial valve. 
