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MEMOIRS OF TTTE UNIVERSITY OF CALIFORNIA. 



The premaxillaries are greatly elongated, extending more than half the total 

 length of the skull. For a little more than half of their length measured back 

 from the anterior end of the rostrum they are united dorsally. Behind the 

 region of contact with each other they are separated by the nasals. 



Figs. 3 and 4. Cymbospondylns petrinus Leidy. Skull X %. Fig. 3, side view; fig. 4, superior view. 

 Pm, premaxillary ; M, maxillary; N, nasal; L, lachrymal; J, jugal; Or, orbit; F, frontal; Pf, 

 pre- and post-frontal; Pto, postorbital; Pr, parietal; Pn, pineal foramen; Sq, squamosal; St, 

 supratemporal ; Q, quadrate; Qj, quadratojugal; Q.f., quadrate foramen; Pt, pterygoid; So, 

 supraoccipital ; Bo, basioccipital ; Ar, articular; An, angular; Sa, surangular; Cn, coronoid; Sp, 

 splenial; D, dentary. 



The maxillaries are longer than in any other described ichthyosaurian, both 

 in relation to the length of the rostral region and to that of the cranium ; and 

 almost, if not quite, half of the dentigerous margin of the upper jaw is situated 

 on these elements. In Mixosaurus the length of the maxillaries is also rela- 

 tively great. 



The superior nares are situated much as in Ichthyosaurus, though appar- 

 ently occupying a slightly more advanced position than in most forms. 



