EASTMAN : CARBONIFEROUS FISHES FROM THE CENTRAL WEST. 185 



Worthen exhibits upwards of 450 teeth disposed in about 18 transverse series, 

 the smallest teeth occurring toward the extremities, and increasing gradually 

 in size toward the middle of the ramus. The series are arranged after the same 

 general pattern as in Cestracion, as is evident from a comparison of the two 

 figures given in Plate 1, Fig. 2 being from a photograph of the lower jaw of 

 Cestracion francisci Girard. 



For a description of the two examples of the symphj'sial series which are 

 known, reference may be had to a previous number of the Museum Bulletin, 

 Vol. XXXIX., No. 3, and it need only be restated here that each individual 



Fig. 10. 



Campodus variabilis (N. & W.). Atchison shales, Cedar Creek, Nebraska. 



syraphysial dentition, X |. 



Lower 



of Campodus possessed at least three series of coalesced anterior or symphysial 

 teeth. As indicated by the marks of contact, there was a median arched 

 azygous series in one jaw, presumably the lower, opposed to which in (jtre- 

 sumably) the upper were two corresponding series separated from each other 

 by a slight interval and mutually interlocking with the former. Each of these 

 series (Text-fig. 10) comprises from 11 to 13 enormously enlarged teeth which 

 are fused into an arch corresponding to that of Edestus and Campyloprion, and 

 to the thrice-coiled spiral of Helicoprion, all of which genera are to be regarded 

 as highly specialized Cestraciont sharks. 



This enlargement of the symphysial series seems to be a hypertrophic char- 

 acter peculiar to Palaeozoic forms, first appearing in the Devonian Protodus, 



