AN ICHTHTOSATJRXrS FROM THE HAS OP WHITBY. 641 



by a strong thickened mass, which, is prolonged outward and a little 

 backward. It curves and becomes bent round in front and is directed 

 forward and greatly compressed from side to side, so as to form the 

 outer posterior border of the temporal foss, where it is 2 inches deep. 

 It is apparently prolonged forward under the postfrontal bone along 

 the length of the temporal foss, though, as already remarked, some 

 doubt may attach to the identification of the bony element which 

 extends behind and below the posterior branch of the post- 

 frontal bone. If it should not be formed by the squamosal it is 

 probably formed by the postorbital, extending upward and expand- 

 ing so as to bind together the other bones posterior to the orbit. 



The supraquadrate hone (sq) has also been called by Prof. Owen the 

 supratemporal and suprasquamosal. It, like the postorbital, is 

 unossified in the Crocodile, in which type the skin extends over the 

 same areas as are here covered by these bones. This supraquadrate 

 I so name because, extending between the squamosal bone above 

 and the quadrato-jugal bone below, it rests upon and hides the 

 quadrate bone in the lateral aspect of the skull. It is subtri- 

 angular in shape, having a vertical measurement of 3| inches, and 

 an antero-posterior measurement of about 4-|- inches. Its posterior 

 border is obscured by matrix ; its superior_ border is comparatively 

 straight, while the oblique inferior border which abuts against the 

 quadrato-jugal is sinuous, the basal angle being broad. Pinally, 

 there remains the quadrato-jugal hone (qj), which has the oblique 

 position of the other bones described and a somewhat triangular 

 outline. Laterally its base is convex from front to back and com- 

 paratively straight in length. It is, as indicated, wedged between 

 the supraquadrate and the postorbital bones, which indent its borders 

 somewhat concavely but irregularly. Its height is 5|- inches and the 

 length of its base is over 4 inches. Behind and below the quadrato- 

 jugal, but entirely anterior in position to it, the articular end of the 

 massive quadrate bone (q) descends and receives a process from the 

 pterygoid bone on its inner side. 



Palatal aspect of the Skull. — The hard limestone forming the 

 matrix of this specimen has been carefuUy chiselled away so as to 

 display the bones of the palate (fig. 3). These elements are beauti- 

 fully distinct in the posterior part of the skull, but anteriorly there 

 has been some little difficulty in making clear the relations of the 

 bones. It follows from the description given that the premaxillary 

 bones (pm) are prolonged outward and backward by the slender bar 

 of the maxillary (m), which is continued by the malar (ma) and 

 quadrato-jugal (qj) to the quadrate (q). This bar becomes somewhat 

 thinner posteriorly, but defines the lateral outlines of the back of the 

 head on its palatal aspect. There are on the palate apparently three 

 pairs of vacuities : — first, a small anterior pair ( V) lying below the 

 exterior nares and between the outer bones of the palate ; secondly, 

 a posterior median pair (SP) divided by the presphenoid bone and 

 lying between the pterygoids ; and, thirdly, a pair of irregular lateral 

 spaces (PTV) between the pterygoids and the malar arch, which 

 extend back to the quadrate bone and are prolonged forward for an 

 Q.J.aS. No. 144, 23f 



