70 BULLETIN: MUSEUM OF COMPAEATIVE ZOOLOGY. 



Campodus. — Symphysial dentition consisting of a median azygons arched 

 series of fused teeth in one jaw, presumably the lower, opposed to which in 

 (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 generaKpattern 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, E. vorax Leidy. 



Gampyloprion. — 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 3j 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. T^'^pe and only known species, H. hessonowi Karpinsky. 



The ancient family of Cestraciontidse, 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 

 Protodiis scoticus (Newton) as founded on the symphysial dentition of 



