ENCHELURTTS. 75 



Description of Specimens. — The type specimen in the Enniskillen Collection 

 exhibits the head with the abdominal region as far as the pelvic fins. It has 

 already been described and figured, loc. cit., and is shown in outline in Text-fig. 18. 

 The only other known specimens are fragments of the trunk, one in the British 

 Museum (PI. XV, fig. 3), the other in the Brighton Museum (Willett Collection 

 no. 105). 



The cranium is exposed from above in the type specimen (Text-fig. 18) and 

 shows its characteristic shape. The postorbital region is crushed at the sides, but 

 seems to have been slightly broader than long ; while the interorbital and rostral 

 regions are very narrow, with indications of a rather large eye. The external 

 bones are smooth, or marked only by lines of growth. The parietals (pa.) are 

 an unsymmetrical pair of irregularly square plates, which clearly meet in the middle 

 line and extend half the length of the postorbital region. They are flanked by the 

 squamosals (sq.), which are relatively large and completely cover the otic region. 



Fig. 17. Halosaurus oweni, Johnson ; about one-third nat. size.— Existing in moderately deep sea. After 



Goode and Bean. 



The frontals (fr.) meet in a w r avy suture, and their narrow interorbital portion 

 articulates in front with the equally narrow mesethmoid (eth.), which is only 

 slightly expanded at its anterior end. There is an ossified ectethmoid or 

 prefrontal (prf.). The quadrate is displaced on the right side of the fossil, and 

 exhibits a small postero-superior cleft, evidently to clasp a symplectic. The 

 entopterygoid (enpt), seen on the left side, is a large laminar bone, slightly more 

 than twice as long as deep. Remains of the premaxillae, beneath the end of the 

 mesethmoid, indicate that they must have been relatively small, with a delicate 

 rod-like extension behind. They distinctly bear minute teeth. The maxilla (nix.), 

 shown on both sides, is relatively very large and closely similar to that of Halo- 

 saurus in general shape. Its anterior portion is a stout narrow bar extending 

 forwards above the premaxilla, while its larger hinder portion is a considerable 

 laminar expansion, not externally ornamented. Its dentition is uncertain. Stout 

 and blunt, small, conical teeth are seen in the chalk above its anterior end, but these 

 may have been borne by another element, The detached and displaced left 



