MORPHOLOGICAL REVISION 



141 



Family LYSOROPHID^ Williston. 

 Genus LYSOROPHUS Cope (page 68). 



Characteristic specimens: Skulls in the Am. Mus. Nat. Hist. Nos. 4696 

 and 4701 ; in the University of Chicago, and in the University at Munich. 



The type in the University of Chicago, Nos. 6526 and 6527, 6528. 

 Numerous specimens of vertebrse in both these institutions. 



In all of the enormously abundant material which has been collected 

 in Texas, but one species of this genus has been recognized, and this species 

 is not distinct from the one described by Cope from Vermilion County, 

 Illinois. The following description is made up from the writings of Cope, 

 Broili, Williston, and Case. 



The skull is small, from 1.5 to 2 centimeters in length and is elongate 

 oval in form. It has no parietal foramen and no temporal fossae. The 

 orbits are lateral and without inferior border. The anterior nares are ter- 

 minal and near the outer edge of the skull. The surface of the skull is smooth, 



Fig. 47. — L. tricartnatus. Nos. 4696-4701 Am. 

 Mus. X 2. Restoration of skull. 



A, Left; B, Posterior surface; C, Superior sur- 

 face; D, Inferior surface. Lettering as 

 usual. 



Fig. 48. — L. tricartnatus. Univ. of Chicago. X 3 circa. 



A. After Williston. Upper view of skull, showing su- 

 tures. Lettering as usual. 



B. Same. Lower view of skull, showing branchial bones. 

 0, otic opening; oc, occipital condyle; pa, neural 

 arches of first vertebra. 



C. Same. X f. After Broili. Lateral view of a mid- 



dorsal vertebra. 



D. Same. Neural spine from above, showing perma- 



nent separation of the two halves. 



without sculpture or rugosities. The various investigators of Lysoropkus 

 seem to be in complete accord as to the position and shape of the bones of 

 the skull, but differ materially in their interpretation. 



The upper surface is composed largely of three pairs of bones, the 

 nasals, frontals, and parietals. • j r 



The nasals are large, paired elements extending to the antenorend ot 

 the skull; the premaxillaries have not been made out, and were evidently 

 very small. The nares lie outside of the nasals and are terminal. 



The frontals are nearly rectangular and extend back as far as the ante- 

 rior edge of the orbit. 



