MERRIAM: TKIASSIC K'HTJI YOSATKIA. 109 



lunate ridge, which tends to have somewhat the form of the spout-like odon- 

 toid process of the Ungulata. Below the prominent inferior ridge the inferior 

 side is not truncated as in specimen 9950, hut a sharply concave area extends 

 around the lower side of the bone between the lunate ridge and the outer mar- 

 gin of the posterior side. The form of the posterior face of the basioccipital 

 in specimen 9913 suggests that the concave face has been secondarily developed 

 on a strongly convex face. 



On the inferior side of the basioccipital there are situated two prominent 

 apophyses similar to those on the inferior face of the basioccipital of Sphenodon. 



The small and somewhat distorted lateral occipital* are seen in place in 

 specimen 9950. They appear to be perforated or notched for the passage of 

 nerves or blood vessels, as in many other ichthyosaurians. In specimen 9913 

 an element possibly representing a lateral occipital rests upon the anterior 

 side of the basioccipital. It has been split longitudinally and shows the pass- 

 age of a large foramen. The complete outlines of the supraoccipital are not 

 shown, but its upper portion is seen to extend forward a considerable distance 

 to form part of the floor of a deep fossa between the posterior arms of the 

 parietals. 



The opisthotic and stapes are not certainly recognized on any of the several 

 specimens that have been carefully examined, but there seems to be some 

 reason for considering that the stapes at least was a less conspicuous element 

 than in the later ichthyosaurs. The opisthotic may be represented by a some- 

 what indefinite element seen in specimen 9950. In the same specimen a slender 

 rod of bone (.r, pi. 5, fig. 1) extending from the otic region to the quadrate 

 may represent the stapes. A careful examination of the well preserved qiiad- 

 rate has not shown the presence of a distinct pit for the accommodation of the 

 distal end of a large stapes such as is present in some of the later ichthyosaurs. 



The heavy quadrate of Cymbospondylus pctrinus is closely and broadly 

 united with the pterygoid, the squamosal, and the quadratojiigal, so that the 

 posterior angle of the skull must have been particularly rigid. The contact 

 with the pterygoid extends inferiorly to the articular head of the quadrate and 

 reaches up to the middle height of the quadrate, where the pterygoid meets the 

 squamosal. The median side of the quadrate which is in contact with the ptery- 

 goid extends forward as a broad plate much as in Sphenodon. On the outer 

 side, the large quadrate foramen is overlapped externally in part by the supra- 

 temporal. The broad articular head of the quadrate is crossed transversely 

 by a marked groove situated between an anterior and a posterior convex 

 surface. 



The general disposition of the typical palatine elements on the inferior 

 side of the skull (pi. 4) is not materially different from that in Ichtltyoxi(n<K. 

 In all cases the palate is largely roofed over, the median margins of the ptery- 



