70 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Campodus. —Symphysial dentition consisting of a median azygous arched 
series of fused teeth in one jaw, presumably the lower, opposed to which mn 
(presumably) the upper is a paired series of similar teeth slightly separated 
from each other and interlocking with the first. These series consist of at least 
thirteen greatly enlarged teeth which are but little laterally compressed, whose 
coronal buttresses are directed anteriorly (ectad), and whose crowns are inclined 
in the same direction, but without being bent so as to override one another. 
Coronal apices very stout and prominent, rather obtuse, their anterior and 
posterior margins sharp and smooth, or but faintly wrinkled. Lateral dentition 
consisting of about 18 transverse series of Orodus-like teeth, arranged after the 
same generalipattern as in Cestracion. Spines and scales unknown. Carbonif- 
erous. Type, C. agassizianus de Koninck. 
Edestus. — Symphysial dentition consisting of a moderately arched series of 
fused teeth, which are fewer in number (5-8) than in the preceding genus, and 
more laterally compressed. The segments are bent forward in such manner 
that the base of each tooth ensheathes those lying next in front. Coronal 
apices prominent, usually acuminate, and with coarsely serrated anterior and 
posterior margins, the latter more steeply inclined than the former. Re- 
mainder of crown (portion corresponding to the lateral extensions of Campodus) 
greatly reduced. Lateral series and other parts of the skeleton unknown. 
Coal Measures. Type, HL. vorax Leidy. 
Campyloprion. — Symphysial dentition consisting of a strongly arched series 
of fused teeth, which are relatively more numerous (14-20 or more) than in 
the preceding genera, higher-crowned, and more laterally compressed. Teeth 
reflected forward so as to override one another toward their extremities, and 
fused for the greater portion of their length. Coronal apices acuminate, ser- 
rated, and more closely apposed to one another than in preceding genera. 
Series traversed by a median longitudinal canal along the base, but without 
lateral grooves. Lateral dentition and other parts of the skeleton unknown. 
Carboniferous. Type, C. annectans Eastman. 
Helicoprion.— Symphysial series consisting of upwards of 150 fused teeth, 
very similar to the last in form, but coiled approximately into 3} whorls. 
The teeth are much laterally compressed, bent forward so as to override one 
another toward the base, and traversed by a double lateral groove as well as 
by a median longitudinal channel along the base. Coronal apices acuminate, 
finely serrated along their anterior and posterior margins, and closely apposed 
to one another. Lateral dentition and other parts of the skeleton unknown. 
Permo-Carboniferous. Type and only known species, H. bessonowt Karpinsky. 
The ancient family of Cestraciontidz, to which these genera belong, 
shares with the Ceratodus-class of Dipnoans the distinction of having 
enjoyed a continuous range from the Devonian to the present day, cer- 
tainly a most remarkable longevity. If we are right in regarding 
Protodus scoticus (Newton) as founded on the symphysial dentition of 
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