FOSSIL AND RECENT 



57 



stt.com 



pmx 



smx 1-2 



qu brr 



sop 



70mm 



Fig. 26. Tarpon atlanticus (Cuvier & Valenciennes). Cranium in left lateral view. 



units. The posterior face of the hypo-, cerato- and epibranchial is covered by two 

 rows of tooth plates. The more dorsal of these is formed by very small plates, 

 irregular in shape and not always set in a linear fashion (indeed this ' row ' is best 

 described as a band of plates). The ventral row is more easily definable with the 

 tooth plates larger and regular in shape and set in a definite row. At the dorsal 

 end of the epibranchial the upper row of tooth plates becomes a broad band which 

 runs in continuity with the ventral row. 



The tooth plates associated with the second and third arches are set in similar 

 fashion to those of the first. The tooth plates associated with the second infra- 

 pharyngobranchial are larger than those on the first. The third infrapharyngo- 

 branchial bears a well-developed tooth plate which lies in series with that associated 

 with infrapharyngobranchial 4. 



The tooth plates upon the fourth arch are similarly distributed to those on the first 

 three, but the most posterior row is formed by plates resembling reduced gill-rakers 

 and these inter digitate with the reduced gill-rakers upon the fifth ceratobranchial. 

 The three tooth-plate rows may still be recognized on the fifth ceratobranchials but 

 the plates of the posterior row have become much enlarged and together form the 

 lower pharyngeals. 



The urohyal extends posteriorly to the level of the fourth basibranchial. An- 

 teriorly it is attached to the lower hypohyal of either side by a short ligament. The 

 gular plate is large, extending for at least half the length of the mandible. 



