FOSSIL AND RECENT 



75 



pto 



mx 



sop 



Fig. 38. Protarpon priscus (Woodward). Cranium in left lateral view. 

 Based on holotype. 



Ventrally the margin of the jaw exhibits a slight inflexion. The surface of the 

 bone in this region is marked by coarse rugae. The dentary forms most of the lower 

 jaw, but posteriorly the articular is produced into a prominent process. The mandi- 

 bular sensory canal pierced the posterior edge of this process and ran through the 

 mandible opening by small pores which become more numerous nearer the dentary 

 symphysis. 



Circumorbital series. The bones of this series are thin and marked only by faint 

 radiating ridges. The first infraorbital is rounded anteriorly and bears a small 

 dorsal prominence which lies posterior to part of the trapezoidal antorbital bone. 

 The antorbital is considerably larger than, and of a different shape from, that element 

 in Tarpon and Megalops. Beneath the orbit the infraorbital bones are narrow but 

 the extent of the second cannot be seen. The third, fourth and fifth members of the 

 series are broad, extending posteriorly over the preoperculum. 



The infraorbital sensory canal runs within the infraorbitals close to the orbital 

 margin, giving off short branches posteriorly. Within infraorbital 1 these branches 

 are numerous and directed posteriorly. 



Opercular series. As a consequence of the posterior quadrate/mandibular articula- 

 tion the preoperculum is composed essentially of a ' vertical ' limb. The bone is 



