MERRTAM: TRIARSIC ICHTHYOSAUEIA. 



25 



eral occipitals is not well known, but they seem to be perforated by large lateral 

 foramina. The supraoccipital extends forward a considerable distance to 



form ;i part of 1 lie Moor of a deep fossa 

 between the posterior arms of the pa- 

 rietals. The form of the opisthotic 

 and prootic are not certainly known. 

 The stapes is not certainly recognized. 

 If represented by an element which 

 lies between the otic region and the 

 quadrate (fig. 6, x) it is much smaller 

 pig. <;. cymbosponw petrinus Leidy. skuii, poste- and more slender than in the later 



rior view, X %. Pr, parietal; Sq, squamosal; St, icllthyOSaUl'S. It may also be noted 

 Hiipratemporal; W, quadrate jugal ; Q, quadrate ; Q.f, 



quadrate foramen ; So, supraoccipital ; Lo, lateral 



o,.,.i,,itai; BO, basioccipitai; s, basisphenoid; x, 



stapes?; Pt, pterygoid; Ar, articular; Sa, surangu- 

 lar; An, angular; Cn, coronoid; Sp, splenial. 



that BO distinct pit for the 



"On of the distal end of the stapes is 



visible On the inner side of the 



Quadrate and Suspensorium. The quadrate is large and heavy and seems 

 to be closely and broadly united with the adjoining elements, making the pos- 

 terior angles of the skull particularly firm. The anterior side of the quadrate 

 overlapping the pterygoid extends forward as a broad plate resembling that seen 

 in the Rhynchocephalia. The face articulating with the mandible is crossed 

 obliquely by a marked depression situated between two strongly convex faces. 

 This form of the articular face on the quadrate has recently been noted also in 

 Ichthyosaurus platydactylus by Broili, 12 and is suggested in Sphenodon. 



The large quadrate foramina perforating the posterior angles of the skull 



Fig. 7. Cymbospondyhis petrinus Leidy. Skull, inferior view, X %. D, dentary; Sp, splenial; Sa, 

 surangular; An, angular; Or, orbit; /, jugal; Qj, quadratojugal; Q, quadrate; So, basioccip- 

 itai; Bs, basisphenoid; Pt, pterygoid; X, ectopterygoid ? ; E, hyoid; PI, palatine; V, prevomer? 



12 Broili, ., Paleontg., Bd. 54, p. 140. 



