132 



ELOPIFORM FISHES 



ynhm 



apal 6C . P 



dpa 



eart 



Fig. 65. Pterothrissus gissu Hilgendorf. Hyopalatine bones, opercular series (stippled) 

 and mandible of right side in medial view. Cartilage hatched. 



lower, mandibular branch opens laterally into a shallow groove mid-way along the 

 length of the shaft. A thin anterior wing is developed in the dorsal half of the hyo- 

 mandibular. There is no overlap of the hyomandibular by the metapterygoid. 

 Instead, there is a large foramen between these bones, the hyomandibular-metaptery- 

 goid foramen, through which passes a deep division of the levator arcus palatini to 

 insert upon the medial face of the metapterygoid. 



The quadrate is basically fan-shaped with the postero-ventral angle produced as 

 a short spine. The ' posterior ' quadrate margin lies horizontally as in most albu- 

 loids. 



The endopterygoid is somewhat longer than broad. A patch of approximately 

 40 teeth, similar in shape to those on the parasphenoid, is borne by the convex 

 palatal surface. The ectopterygoid of Pterothrissus, unlike that of Osmeroides, is 

 narrow and only meets the endopterygoid over a short distance (Text-fig. 64) . The 

 ectopterygoid bears a few tiny teeth which are difficult to see in ' unprepared ' 

 specimens. Dorsally the ectopterygoid process is relatively small and is directed 

 towards the infraorbital bones. A short ligament connects the process with the 

 infraorbital series at the junction of the first and second infraorbitals. 



There is no ossified autopalatine. The palatine cartilage articulates with the 

 mesethmoid by a simple rounded head, the anterior process of the palatine. Beneath 

 the lateral ethmoid there is another dorsally directed process, the posterior process 

 of the palatine. The dermopalatine is represented by a small, toothless, oval 

 ossification attached to the ventral surface of the palatine cartilage. 



Dermal upper jaw. The premaxilla is stout with an inwardly turned head bearing 

 a single articulatory facet. A tough ligament runs from the external face of the 



