FOSSIL AND RECENT 



ace 



105 



pee 



vhh 



10mm 



Fig. 51. Osmeroides lewesiensis (Mantell). Hyoid bar and branchiostegal rays of 

 left side in lateral view. From B.M.N. H. P. 5680. 



the postero-lateral aspect. Upon the medial surface the articular bears a prominent 

 ledge which is continued for a short distance on the dentary. The dorsal surface 

 of this ledge is grooved and provided an attachment area for muscle fascia. In 

 0. levis there is a small sesamoid articular resting on the ledge of the articular ; such 

 an element was not seen in 0. lewesiensis, but this is probably due to imperfection 

 of the specimens. Much of the articulatory cup is formed by an endosteal articular 

 which extends forward as a narrow splint overlying the articular ledge. 



Circumorbital series. There are eight circumorbitals of which one, the supra- 

 orbital, is anamestic. The supraorbital is a long, narrow bone which lies, for the 

 greater part of its length, in a narrow rebate on the frontal. The surface is orna- 

 mented in the same fashion as the frontal. The ventral end of the supraorbital 

 contacts the small triangular antorbital. 



The first infraorbital (lachrymal) is large with a rounded anterior border. The 

 ventral margin overlaps the dorsal extent of the maxilla while dorsally there is a 

 small rounded projection. The second infraorbital expands posteriorly where it 

 meets the third in an oblique suture. The third, fourth and fifth infraorbitals are 

 all wider than deep. A dermosphenotic was not seen in 0. lewesiensis, but the gap 

 left between the last infraorbital and the frontal suggests that one was present. 

 No definite evidence of rostral ossicles could be found in any of the specimens 

 examined. 



Hyoid arch, branchiostegals and gular plate. Both the anterior and posterior 

 ceratohyals are stout, the former being three times as long as the latter. The 

 posterior ceratohyal shows a notch postero-dorsally which received the ventral end 



