Osteology of Catuvus and OsteorachiS. 595 



pterygoid bones are too imperfect for description; but tlie 

 entopterygoid is clearly thin, expanded, and laminar, with 

 fine granulations on its oral face (PI. IX. fig. 1 a, enpt.). 

 Another stouter bone, which is deepened in front and bears 

 a series of large teeth on its outer inferior margin, may be 

 the ectopterygoid (PI. IX. fig. 1, ecpt.). The palatine on its 

 inner face appears as a small lamina of bone below the ento- 

 pterygoid, and on its oral margin, which is apposed to the 

 maxilla, there is a single series of large teeth (PL VIII. 

 fig. 4 a, pi.) ; but viewed from without (PL VIII. fig. 4, /j/.) 

 this element is shown to be in reality of robust proportions, 

 interposed as usual between the maxilla and prefrontal. The 

 maxilla (PL VIII. figs. 3, 4, mx,) is much elongated, some- 

 what deepened behind, thickened in front, and bearing a long 

 inwardly and anteriorly directed process immediately in 

 advance of its palatine articulation. Its oral border forms 

 an irregular concave arch, and bears a single series of teeth, 

 which are smallest behind ; the hinder portion of its upper 

 border exhibits a facette (PL VIII. fig. 4,/.), whicli is over- 

 lapped by an elongated supramaxillary plate (PL VIII. 

 fig. 3, s.mx.). The premaxilla (PL VlII. fig. 3, prnx.) 

 exhibits an extended oral border, with a series of teeth larger 

 than those of the maxilla; the nature and limits of its 

 ascending ])rocess cannot be satisfactorily observed. The 

 mandible (PL VIII. fig. 3 ; PL IX. figs. 1, 1 a) is very 

 narrow at the symphysis, has a nearly straight inferior border, 

 and gradually rises into a high coronoid region near its hinder 

 end ; it comprises four, perhaps five, distinct elements. The 

 long dentary (PL VIII. fig. 3 ; PL IX. figs. 1, la, d) occu- 

 pies the greater portion of the outer aspect, meets its fellow 

 of the opposite side at the symphysis, rises behind into the 

 coronoid, and bears a single series of relatively large teeth. 

 The splenial (PL IX. fig. I «, s/j/.) extends about as far as 

 the dentary on the inner side of the ramus, and is much 

 thickened where it enters the symphysis ; its teeth are all 

 very small, and for at least the anterior half of the bone they 

 are arranged in a single series, while beyond they appear to 

 be clustered. The angular element {aj.) is large, forming 

 the greater part of the coronoid region, and immediately above 

 it is an elongated coronoid bone [cor.) completing the eleva- 

 tion. The articular [ar.) exhibits a convex facette at the 

 extreme hinder end of the mandibular ramus, but whetlier or 

 not this element is fused with the angular is as yet undeter- 

 mined. The epihyal (PL IX. figs. 1, 1 a, ep.h.) is small and 

 triangular in form, with a robust facette near the hinder end 

 of its upturned margin j its extreme length is scarcely more 



