FOSSIL AND RECENT 



67 



all of the periotic bulla, leaving no space for the posterior passage of the jugular vein. 

 The jugular vein has therefore to take a different course from that seen in most 

 elopiforms. The vein leaves the pars jugularis above the level of the prootic- 

 intercalar bridge and runs for a short distance along the floor of the subtemporal 

 fossa before passing postero-ventrally through a foramen which represents the space 

 left between the prootic-intercalar bridge and the exoccipital (cf. a similar foramen 

 in Elops, p. 12), and leaves the cranium by a foramen between the intercalar and 

 the exoccipital (Greenwood 1970a: pi. 2, ophv). This condition is rather different 

 from that seen in Tarpon which has been described above. The position of the jugu- 

 lar vein opening in the prootic of Tarpon is primitive. Posteriorly, the jugular vein 

 of Tarpon has a slightly different relationship to the intercalar. The jugular vein 

 runs back in a groove which is entirely surrounded by the intercalar, there being no 

 contribution by the exoccipital. In short, the jugular vein leaves the cranium of 

 Megalops between the exoccipital and the shield-like expansion of the intercalar, 

 whereas in Tarpon its exit is surrounded by the basal, crescentic and shield-like parts 

 of the intercalar. 



pto 



pmx 



101 



oen 



m s 



20mm 



qu iop sy 



Fig. 32. Megalops cyprinoides (Broussonet). Cranium in left lateral view. 

 Based on B.M.N.H. 1876.3. 11. 1. 



