oa) 
36 PALEOZOIC PALEONTOLOGY. 
crossed also by much finer, crowded, concentric striz. Brachial valve 
not seen, but it is apparently deeply concave. 
The dimensions of the best specimen observed are: length, 12 mm. ; 
width, 17 mm.; convexity, 6 mm. | 
Remarks.—In common with most of the Onondaga limestone 
fossils, this species is represented only by fragmentary specimens. 
The New Jersey specimens are smaller than the typical New York 
representatives of the species as illustrated in the New York 
Paleontology, but they seem to agree with the characters of C. 
arcuatus more closely than with any other species. The species may 
be recognized by its fine, radiating markings and its slight mesial 
flattening or depression of the pedicle valve. 
RHIPIDOMELLA VANUXEMI (Hall). 
Plate LI., Figs. 5-7. 
1867. Orthis vanuxemi Hall, Pal. N. Y., vol. IV., p. 47, pl. 6, figs. 
3 a-r. 
Description.—Shell subcircular or suboval in outline; hinge-line 
much shorter than the greatest width of the shell; cardinal extremities 
rounded. Pedicle valve depressed-convex on the umbo, flattened or a 
little concave toward the lateral and front margins; beak small, ex- 
tended but little beyond that of the opposite valve, but little incurved ; 
cardinal area small, concave. Brachial valve convex; the beak scarcely 
extended beyond the cardinal border. Surface of both valves marked 
by fine, crowded, rounded costa, which increase by bifurcation and by 
intercalation; and by fine, concentric striz, with a few stronger, sub- 
lamellose lines of growth. 
The dimensions of an average middle Devonian specimen are: 
length, 19 mm.; width, 20 mm.; thickness, 8 mm. 
Remarks.—Numerous fragmentary specimens of Rhipidomella, 
which may be referred to the species R. vanuremt, are sometimes met 
with in the Onondaga limestone of New Jersey, but no specimens 
approaching completeness have been observed. The description of the 
species here given has been drawn up from more perfect New York 
specimens. 
