DEVONIAN FAUNAS. 
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RHYNCHONELLA TRANSVERSA Hall. 
Plate XNIX., Figs. 28-31. 
1859. Rhunchonella transversa Hall, Pal. N. Y., vol. IIL, p. 234, pl. 
34, figs. 9-16. 
Description.—Shell subtriangular in outline, wider than long, the 
postero-lateral margins meeting at the beak in an angle of 90° or a 
little more. Pedicle valve depressed-convex, most prominent on the 
umbo; depressed anteriorly in a rather broad, rounded sinus; the 
beak pointed, incurved over that of the opposite valve. Brachial valve 
more convex than the pedicle, flattened on the umbo, elevated an- 
teriorly in a prominent mesial fold. Surface of each valve marked 
by about fifteen simple, angular plications, which extend to the beak, 
about three of them being included in the fold and sinus. 
The dimensions of an average-sized individual are: length, 8 mm. ; 
width, 10 mm.; thickness, 5.5 mm. 
UNCINULUS MUTABILIS (Hall). 
Plate XXIX., Figs. 1-5. 
1859. Rhynchonella mutabilis Hall, Pal. N. Y., vol. III., p. 225, 
pl. 29, figs. 4 a—-o, pl. 30, figs. 1 a—-e, 2 a—r. 
Description.—Shell subglobose, usually longer than wide. Pedicle 
valve strongly convex, most prominent on the umbo; beak small, 
pointed, closely incurved over that of the opposite valve, the anterior 
margin produced into a linguiform extension nearly at right angles 
to the plane of the valve and fitting into a corresponding sinus in the 
margin of the brachial valve. The mesial portion of the valve, op- 
posite the lingual extension, slightly depressed anteriorly into a 
shallow, more or less inconspicuous mesial sinus. Brachial valve 
usually a little more convex than the opposite one, its beak closely 
incurved under that of the pedicle valve. ‘Toward the front its mesial 
portion is slightly elevated in an indistinct, depressed fold. Surface 
of each valve marked by twenty-two to twenty-eight depressed, 
