9 8 



ELOPIFORM FISHES 



SOC 



exo 



10 mm 



f uv 



Fig. 47. Osmeroides lewesiensis (Mantell). Neurocranium in posterior view. 

 Based on B.M.N.H. P.6456. 



of the post-temporal fossa. The horizontal semicircular canal within the pterotic 

 is indicated externally as an arch-shaped swelling immediately beneath the hyo- 

 mandibular facet. 



In posterior view the pterotic is seen to form part of the roof and the entire lateral 

 border to the opening to the post-temporal fossa. 



The epiotic forms part of the dorsal and the entire medial margin of the opening 

 of the post-temporal fossa. Internally the epiotic forms a small portion of the medial 

 wall of the fossa. Dorsally the epiotic is produced as a rounded process which re- 

 ceives the upper limb of the post-temporal. The posterior surface of the epiotic 

 is deeply excavated, the excavation being continuous with that on the exoccipital 

 and together forming a sub-epiotic fossa. 



The supraoccipital is pentagonal in posterior view. Dorsally this bone separates 

 the epiotics while ventrally it partially separates the exoccipitals. There is a very 

 small supraoccipital crest. Internally the supraoccipital is continued forward as 

 two antero-lateral wings which form much of the medial wall of the post-temporal 

 fossa of either side. 



The exoccipital meets its partner in the mid-line above and below the foramen 

 magnum. Adjacent to the foramen magnum the exoccipital is produced posteriorly 

 into a structure resembling a neural arch. The lateral face of the exoccipital forms 

 part of the subtemporal fossa, the ventral edge of which is defined by a weak ridge 

 on the exoccipital. Posteriorly, beneath the level of the intercalar, the exoccipital 

 is pierced by the large, posteriorly directed vagus foramen. Smaller foramina 



