226 PALEONTOLOGY 



is quadrate ; thence it contracts laterally to near the maxillo- 

 premaxillaiy suture, where it continues either parallel or with 

 a slight swelling before rounding into the obtuse anterior 

 termination. 



The orbits are at or near the middle of the skull : estimat- 

 ing the length of this by that of the lower jaw, they are in 

 advance of the middle part in Plcsiosaurus HawMnsii. The 

 orbits are rather subtriangular than round, being somewhat 

 squared off behind, straight above, and contracted anteriorly. 

 No trace of sclerotic plates has yet been discerned in any 

 specimen. The temporal fossa? are large subquadrate apertures. 

 The nostrils, which are a little in advance of the orbits, are 

 scarcely larger than the parietal foramen. Beneath them, upon 

 the palate, are two similar-sized apertures, probably the palatal 

 nostrils. 



The lower jaw presents an angular, surangular, spleniaL 

 and dentary element, in each ramus; the dentary elements 

 being confluent at the expanded symphysis. There is no 

 vacuity between the angular and surangular or any other 

 element of the jaw. The coronoid process is developed, as in 

 Placodus, from the surangular, but rises only a little higher 

 than in crocodiles. The alveoli are distinct cavities, and there 

 is a groove along their inner border in both jaws. 



When the successional teeth first project in that groove, 

 they give the appearance of a double vow of teeth. All the 

 teeth are sharp-pointed, long, and slender, circular in cross 

 section, with fine longitudinal ridges on the enamel ; the 

 anterior teeth are the longest . 



The scapula is a strong triradiate bone, the longest ray 

 being formed by the acromial or clavicular process, which 

 arches forward and inward to abut againsl the sternum or 

 epicoracoid. 



The proper body of the scapula is short and straight, 



* This is omitted in mosl of the published restorations of the Plesiosaurvs. 



