FOSSIL AND RECENT 47 



parietal. The surface of the frontal is marked by a very shallow ridge which runs 

 the length of the bone and extends posteriorly on to the parietal. 



Anteriorly the supraorbital canal is contained within a horizontal plate-like 

 nasal. In smaller individuals the nasal is tubular, as in Elops. Above the orbit 

 the frontal has a narrow rebate for the narrow supraorbital. In larger specimens 

 the supraorbital is tightly bound to the frontal. 



The parietal is three times as long as wide and is overlapped by the frontal an- 

 teriorly. During growth the shape of the parietal changes from broad to narrow. 

 The pterotic is triangular and its true extent may not be seen in dorsal view, due to 

 the convexity of the skull roof. 



Beneath the dermethmoid the ethmoid cartilage extends back to the orbit. 

 Anteriorly, where the cartilage projects beyond the dermethmoid, it becomes ossified 

 as it expands over the dorsal part of the vomer. This ossified mesethmoid is securely 

 attached to the vomer, so that its individuality may only be recognized in young, 

 alizarin-stained specimens. The dorsal surface of the mesethmoid bears a median 

 ridge on either side of which is an ovoid depression. The depression receives 

 the head (cranial condyle) of the maxilla, while the premaxillae meet one another 

 immediately above the median ridge. 



The medial wall of the nasal capsule is mainly cartilaginous. The lateral ethmoid 

 is ossified in the lateral part of the planum antorbitale. From its sutural connection 

 with the underside of the frontal the lateral ethmoid curves anteriorly and ventrally 

 to contact the dermethmoid wing. The ventral surface of this contact bears a large 

 cartilaginous meniscus which receives the dorsal surface of the palatine head. 



The vomer underlies the mesethmoid and the anterior end of the parasphenoid. 

 In ventral view it is diamond-shaped with the posterior angle produced in an 

 elongated point which interdigitates with the parasphenoid. The dorsal surface 

 of the vomer contributes to the facet receiving the maxillary head. The vomer 

 bears an ovoid patch of numerous fine, backwardly pointed teeth. The confluence 

 of paired vomerine tooth plates is more complete in adult Tarpon than in Elops, 



From the vomer the parasphenoid narrows beneath the orbit before expanding 

 at the level of the ascending wings. Posteriorly the parasphenoid tapers and 

 divides into two prongs which end below the posterior part of the basioccipital. 

 The gap between these two prongs represents the anterior part of a groove beneath 

 the basioccipital and the first vertebral centrum. The dorsal aorta runs in this groove 

 and divides into the lateral dorsal aortae at its anterior end. Such a groove is clearly 

 necessary in this form since the swimbladder diverticulum is pushed tightly against 

 the skull base beneath the basioccipital. Beneath the ascending process the 

 parasphenoid is produced laterally in a small prominence at the apex of which the 

 internal carotid artery enters the myodome. Immediately anterior to this promi- 

 nence a shallow groove curves antero-ventrally and marks the cranial origin of the 

 adductor arcus palatini musculature. A very narrow band of small granular teeth 

 is found on the parasphenoid beneath the orbit. In all megalopids the parasphenoid 

 tooth patch is less extensive than that of the Elopidae. 



The pterotic forms the posterior part of the hyomandibular facet and the dorsal 

 region of the subtemporal fossa. The posterior face of the pterotic forms the roof 



