150 



MAEINE REPTILES OF THE OXFOED CLAY, 



missing. Some of the elements are so little distorted that it has been possible to join 

 them together again in their natural position, as in the case of the basis cranii and the 

 pterygoids shown in test-figure 74. The general form of the skull, as a whole, cannot 

 be made out with certainty, but it must have been very similar to that of Murcenosaurus 

 (text-figs. 46, 47), since the individual bones are for the most part like the corresponding 

 elements in the skull of tliat genus. In consequence of this general similarity the 

 bones will not be described in detail, except where they present peculiar features. 



In the hasioccipital (text-figs. 73-74) the occipital condyle {oc.c.) is more strongly 

 convex, and the pterygoid processes are relatively larger than in Murcenosaurus. The 

 united exocci^ntal and oinsihotic (text-fig. 72) are not so stout, and the paroccipital 



p.rof 

 h.c. 



J^9 



J'^S 



Eight esoccipitaUopisthotie of Trideulus seelci/i : A, from inner side; B, from outer side; 



C, from front. (E. 3539, nat. size.) 



Of., cavity for ampulla of posterior vertical semicircular caual; boc.f., facet for union with the hasioccipital; 

 Zf.c, channel for horizontal semicircular canal; jv(j., jugular foramen; pro.f., surface for union with 

 prootic ; p.v.c, channel for posterior vertical semicircular canal : ([.f., facet for quadrate ; soc.f., surface 

 for union \^■ith supraoccipital ; sut., line of juncture between the eioccipital and opisthotic ; XII, foramen 

 for the XII nerve. 



processes, the distal ends {q.f.) of which are much expanded, are longer and more 

 slender than in Mwcenosaurus. The line of union (sut.) between the exoccipital and 

 opisthotic elements is clearly traceable on the inner face and on the surfaces for union 

 with the basi occipital (hoc.f.) and supraoccipital (soc.f.) bones. The various cavities 

 and foramina for the nerves, blood-vessels, and auditory apparatus are much as in 

 Murcenosaurus (cf. text-fig. 45). The supraoccipital is not known. 



The hasisplienoid [hs., text-figs. 73, 74), as in Murcenosaurus, consists of a thickened 

 posterior body and an anterior portion, the upper surface of which is deeply hollowed 



