AN ICHTHTOSAITRUS PBOM THE LIAS OF, WHITBY. 



647 



Fig. 4. Outline of polished anterior end of the section of the jaws, showing 

 teeth in the premaxillary bones, and the vomerine bones shaded 

 occupying the median line of the palate. 



In all the figures the lettering is the same : — 



TF. Temporal fossa. 



q. Quadrate bone. 



FP. Foramen parietale. 



ho. Basioccipital bone. 



0. Orbit. 



bs. Basisphenoid bone. 



N. Anterior nares. 



ps. Presphenoid bone. 



pm. Premaxillary bone. 



p. Pterygoid bone. 



m. Maxillary bone. 



pn. Palatine bone. 



n. Nasal bone. 



t. Transverse bone. 



I. Lachrymal bone. 



V. Vomer. 



ma. Malar bone. 



8P. Sphenoido-pterygoid vacui- 



pf. Prefrontal bone. 



ties. 



/. Frontal bone. 



PTV. Vacuity between the trans- 



pt. Postfrontal bone. 



verse and palatine bones. 



p. Parietal bone. 



V. Vacuity in the position 



sqm. Squamosal bone. 



usually occupied by the 



aq. Supraquadrate bone. 



posterior nares. 



qj. Quadrato-jugal bone. 



X. Matrix. 



jpo. Postorbital bone. 





