Genus Lysorophus, Cope. 23f> 



which agrees pretty closely with Broili's. I consider 

 v. Huene in error in regarding that there are " two large, 

 elongate internal nares, separated by a narrow bridge." The 

 large supposed left choana of v. Huene I regard as the 

 median vacuity between the prevomers, and the narrow 

 bridge as the right prevomer. The figure I give will show 

 how I interpret the palatal structures. The prevomers form 

 a horseshoe-like arrangement with posterior processes passing 

 back to the parasphenoid and apparently articulating with 

 the pterygoids. The teeth on the prevomers are well shown 

 in this specimen. In front there are about 6 and about 

 8 on each side. The palatines are delicate bones extending 

 from the maxillae to the pterygoids. Between the palatines 

 and prevomers are, I believe, the internal nares. The ptery- 

 goids extend back as rather delicate bones to meet the 

 quadrates. The pai'asphenoid is a very large bone, which 

 forms nearly the whole of the base of the posterior two- 

 thirds of the skull. The supposed suture figured by 

 v. tluene between the parasphenoid and the basisphenoid 

 is, I think, a fracture merely. 



The figure I give of a transverse section of the skull 

 (fig. 3) shows the relations of the pterygoid, to the para- 

 sphenoid, and also the elements of the back of the mandible. 



In Broili's figure A of the side view of the skull, there are 

 seen in the orbital region some deep-seated elements. These 

 are also shown in two of the American Museum specimens. 

 In what might be regarded as the sphenethmoid region 

 there appear to be three elements with a deep posterior 

 notch. In one of the New York specimens an almost 

 exactly similar appearance is shown, and further back an 

 elongated element very like an epipterygoid in appearance. 

 Though these elements have been seen by Broili, neither he 

 nor anyone else appears to have expressed any opinion as 

 to what they were. After considering many possibilities I 

 have come to the conclusion that they are ossifications or 

 calcifications in the cartilaginous brain-case. The anterior 

 elements look as if separated by sutures, but, whereas all 

 true sutures in the skull and even cracks are filled with the 

 red clayey matrix, these divisions are formed of clear calcite 

 which probably indicates that they were originally formed 

 by hyaline cartilage. Further, in a second specimen the 

 ossification appears to be entire. The posterior narrow 

 vertical element is also, in my opinion, an ossification of 

 the cranial cartilage. It certainly has much superficial 

 resemblance to a reptilian epipterygoid. It articulates with 

 the parietal above and passes down to at least near to the 

 pterygoid. It thus answers in position to the epipterygoid. 



