FASTMAN: 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 francisce Girard. 
| For a description of the two examples of the symphysial 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. Lower 
symphysial dentition, < 4. 
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 (pre- 
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, 
