332 
SELACHII. 
The jaw shown in the accompanying woodcut (fig. 13), is some¬ 
times termed upper \ and sometimes lower 1 2 . In his latest remarks 
upon the subject, Sir ltichard Owen states that it represents the 
lower dentition, which differs from the upper in the presence of an 
azygous series of symphysial teeth. So far, however, as the present 
writer has had the opportunity of observing, this character is not 
constant. 
Fig. 13. 
Jaw of Cestracion jphilippi.— Recent. 
In the living species the pterygo-quadrate cartilage articulates 
with the preorbital region of the cranium, but it is impossible to 
determine whether such was the case in the extinct species here 
referred to the same genus. 
Cestracion falcifer, Wagner. 
1852. Cestracion, F. A. Quenstedt, Handb. Petrefakt. p. 178. 
1857. Cestracion falcifer, A. Wagner, Gelehr. Anz. bay. Akad. Wiss. 
vol. xliv. p. 290. 
1863. Acrodus falcifer, A. Wagner, Abh. k. bay. Akad. Wiss., math.- 
phys. Cl. vol. ix. p. 301, pi. v. fig. 1. 
1 R. Owen, Palaeontology, 2nd edit. (1861), p. 127, fig. 41. 
2 R. Owen, Gfeol. Mag. vol. vi. (1869), p. 196. 
