FOSSIL AND RECENT 205 



medial side of which the levator arcus palatini inserts. The albuloids possessing 

 the above mentioned foramen do not show such a ridge. The only other ' lower ' 

 teleosts I have examined in which there is a comparable foramen are Chaetoessus 

 and Chanos, but in these forms there is apparently no passage of musculature 

 through this aperture. 



The ectopterygoid of albulid and pterothrissid fishes is produced dorsally into a 

 well-defined process which lies against, and supports, the flimsy infraorbital bones 

 beneath the orbit. A comparable structure is found in most elopiforms but it never 

 reaches the same proportions as in the albuloids. In 0. latifrons this ectopterygoid 

 process, although a rudimentary spine-like structure, is set in typical albuloid 

 fashion. Elsewhere an ectopterygoid process is rare but does occur in the clupeid 

 Dussumieria (Ridewood 1904). 



The palatine is, as in all elopiforms, composed of distinct endoskeletal and dermal 

 components. The former is often cartilaginous (ossified in 0. lewesiensis) and 

 articulates with the neurocranium at two points, anteriorly with the mesethmoid or 

 ethmoid cartilage and posteriorly with the lateral ethmoid. Among elopiforms, 

 the lateral ethmoid projection of the palatine is only found in albuloids. Such a 

 palatine-neurocranial connection gives some rigidity to the palate. Elsewhere, a 

 close and rigid juxtaposition of palatine and lateral ethmoid is found in predatory 

 fishes taking large prey such as the Chirocentridae and, presumably, the fossil 

 Ichthyodectidae, and is a development in response to a strong biting force. 



The upper and lower jaws of the Albulidae and Pterothrissidae are distinctive and 

 produce an inferior mouth suitable for bottom feeding. Osmeroides shows a terminal 

 mouth (the condition in 0. latifrons is not known) while in Lebonichthys and Istieus 

 it is only slightly inferior. The inferior mouth is produced by a combination of 

 snout elongation and shortening of the lower jaw. Jaw teeth of later albuloids are 

 found only on the premaxilla and dentary (a few maxillary teeth remain in Istieus 

 and Pterothrissus) and the reduced maxilla supports a single supramaxilla. 



The premaxilla is firmly bound to the ethmoid region by ligaments and is capable 

 of only the slightest lateral movement. The head of the maxilla is turned sharply 

 inwards and in the Albulidae and Pterothrissidae there is no separate palatine process 

 on the maxilla as there is in the Osmeroididae and the Elopoidei. Instead, the 

 rounded palatine head fits against the rear of the maxillary head. The maxilla of 

 Recent albuloids is capable of limited independent movement ; only when the mouth 

 is fully open does it enter the gape. 



The dentition of the Albulidae and Pterothrissidae is significantly different from 

 the primitive type seen in 0. lewesiensis. In albulids and pterothrissids the dentition 

 borne by the maxilla and the premaxilla consists of a broad band of needle-like teeth 

 in contrast to the small villiform teeth borne by these elements in 0. lewesiensis. 

 The shape of the teeth of 0. latifrons is intermediate. 



The palatal dentition is different in each of the three albuloid families. The 

 Osmeroididae are primitive in having small, villiform teeth on the parasphenoid, 

 dermopalatine, endopterygoid, ectopterygoid, basihyal and basibranchial. The 

 teeth of 0. lewesiensis and 0. levis are more or less uniform in size but those of 0. 

 latifrons differ both in size and shape. The albulid dentition is modified for crushing 



