LEPIDOTUS. 



41 



tig. 1, hm.) is a narrow lamina of bone, with a broad prominence behind for the 

 support of the opercuUim, and strengthened below this on the outer face by a 

 longitudinal ridge. The metapterygoid (PI. VIII, fig. 1, mpt.) is imperfectly 

 known, but is a relatively large thin lamina of bone probably shaped almost as in 

 Amid. The entopterygoid has already been mentioned as a thin toothless lamina 

 seen in section in Text-fig. 16, enpt. The ectopterygoid, though thin and toothless 

 at its hinder end (Text- fig. 16, expt.) and rising above into a longitudinal sharp 



Fig. 17. — Lepidotus mantelli, Agassiz ; diagram of arrangement of teeth in upper (A) and lower (B) 

 jaws, about nat. size. — Wealden : Sussex, d., dentary; ^J^., pterygo-palatine ; sjsL, splenial ; v., 

 vomer. From Catal. Foss. Fishes, Brit. Mus., pt. iii, lcS9.j. 



crest throughout its length (PI. XI, fig, 3 a), is much thickened at the oral border 

 to bear the powerful dentition, and seems to be completely fused in front with the 

 equally thickened palatine, which abuts against the vomer. The slightly concave 

 oral face of the pterygo-palatine thus formed bears the irregular longitudinal 

 series of teeth, of which the inner are the largest and the most anterior are the 

 smallest (PL XI, figs. 3, 4). An outer fourth row of very small teeth is sometimes 

 present. The single vomer (PI. XI, figs. 2, 4) is also much thickened (fig. 2 6), 

 and its long and narrow oral face bears teeth almost as far Imck as the hinder 

 limit of teeth on the ectopterygoids. The vomerine teeth are irregularly arranged, 

 but the largest are in two pairs behind, and they decrease in size forwards, where 

 they are in four or even five longitudinal rows. The maxilla is a relatively small 

 and delicate lamina of bone, forming a deep expansion behind but tapering forwards 



6 



