206 DE. W. G. EIDEWOOD ON TUE CEANIAL OSTEOLOGY OF 



with the lower hypohyals, are attached in Notopterus to cartilage 

 below the level of the single hypohyal bones. The glossohyal is 

 large and well ossified on the surface, although cartilage persists 

 in tlie interior, there being no endosteal glossohyal ; it bears 

 large, strongly curved teeth around its edge. The first basi- 

 branchial is unossified. Above the first, second, and third 

 basibranchials is a membrane-bone which bears small crowded 

 teeth over nearly the whole of its upper surface. Small teeth 

 also occur on the fifth ceratobranchials. The first pharyngo- 

 branchial is amall and cartilaginous, and there is no spicular bone. 

 The urohyal is rather short and broad, and a pair of ossified 

 tendons, similar in structure and function to the urohyal, and 

 together nearly equalling the urohyal in size, project downward, 

 outward, and backward from the lower surface of the posterior 

 end of the second basibrauchial. 



Htodontid^. 



Hygdok alosoides. 



Grankim (Pi. 25. figs. 19, 20, and 21). — The characteristic ap- 

 pearance of the cranium is due to the low position of the anterior 

 three-fourths of the parasphenoid. This part is curved and 

 strongly toothed, and makes a distinct angle with the posterior 

 part. The parasphenoid underlies but a small portion of the 

 basioccipital, and the eye-muscle canal opens at its posterior 

 end by an oval foramen. The vomer is small and edentulous. 



The ethmoid region is short. The frontals also are rather 

 short, and the parietals are consequently more anteriorly placed 

 than usual. The two parietals meet in the middle line, but only 

 for a short distance. The supraoccipital separates the hinder 

 parts of the parietals, and possesses a crest which is T-shaped in 

 transverse section. Each of the exoccipitals has a vertical wing 

 situated at the side of the foramen magnum. The opisthotic is 

 rather large, and forms the greater part of what at first glance 

 appears to be the squamosal spine. The opisthotic forms part 

 of the articular cavity for the posterior head of the hyo- 

 mandibular, which fact is exceptional. 



A side view of the cranium shows an oval tract of cartilage 

 bounded by the epiotic, parietal, and squamosal. This is not 

 to be confounded with the lateral foramen of Notopterus and the 



