514 E. TTJLLEY NEWTON ON THE REMAINS OF 



groove, as is shown by the part which is still preserved. Ante- 

 riorly the mandible is truncated by the peculiar symphysis, which 

 occupies nearly the entire depth of the jaw (PI. XXII. fig. 6), and, 

 as seen in a side view (figs. 1 and 5), is set obliquely to its general 

 direction. The symphysial surfaces are rugose, and show that car- 

 tilage must have occupied a space between the two rami. The 

 dentary margin presents two depressions and three prominences 

 (fig. 1), the latter marking the positions of the larger teeth. Ante- 

 riorly there are two large teeth (nearly | inch diameter), which are 

 succeeded by a small one (about -^ inch diameter) and two of 

 median size (about | inch diameter). Next follow three largo 

 teeth, the first and last as large as, or larger than the two at the front 

 of the jaw. Succeeding these there are eleven teeth preserved in 

 situ, and spaces for probably six or seven others ; they vary in size 

 from T X B to J of an inch diameter. The thinning away of the den- 

 tary bone behind these teeth shows clearly that it terminated here ; 

 and the total number of teeth, therefore, could not have exceeded 

 twenty-six or twenty-eight. The teeth are slightly oval in trans- 

 verse section ; and the portion projecting above the jaw is highly 

 polished. The larger teeth, when held so as to catch the light, show 

 very obscure annular markings. The greatest peculiarity of these 

 teeth is the remarkable manner in which their extreme points are 

 bent inwards. This is not seen when the jaw is viewed from the 

 side, but is very marked when the teeth are seen from before or 

 behind (figs. 1 a, 1 6). This character of the teeth does not appear 

 to be present in P. lestrio ; for Prof. Cope makes no mention of it, 

 although he speaks of one of his specimens as having nearly com- 

 plete dentition ; and such an evident peculiarity could not have 

 escaped observation. 



Hyoid. — Prof. Cope says with regard to the hyoid of Portheus and 

 its allies (7. c. p. 185) : — " Little can be said respecting the hyoid 

 apparatus in this family. Some inferior branchihyals, preserved in 

 Portheus thaumus, are short flat rods. Two long flat bones, in place 

 between the dentaries of a P. lestrio, appear to be the distal cera- 

 tohyals. They terminate in some crushed basihyals, and are 

 covered with minute teeth en brosse on the inner faces and superior 

 margins." 



Several elements of the hyoid apparatus are preserved in the 

 Gault specimen, and occupy very nearly their normal positions, 

 being wedged in between the rami of the mandible. These bones 

 are partly shown in Plate XXII. fig. 1, but are much better seen 

 from the opposite side when the right ramus is removed (fig. 5). 

 The form of the large bone thus seen (ch), and the position which 

 it occupies, indicate that it is the right ceratohyal (the left bone is 

 in place, but hidden in this view). These bones are very thin and 

 compressed, especially at their anterior extremities. Posteriorly 

 each has a considerable vertical extent ; but this gradually decreases 

 anteriorly for about |- of its length ; then the anterior fifth suddenly 

 widens again to nearly the same dimensions as the posterior part, 

 and terminates in a fanlike extremity. Both ends of this bone have 



