198 DE. W. G. EIDEWOOD ON" THE CKAISTIAL OSTEOLOGY OP 



Mormyroids, and it is covered by a thin scale-like supratemporal 

 (No. 12 of Erdl's figure). The postfrontal is small, and is 

 wedged in between the front part of the squamosal and the 

 upper edge (there is no proper articular facet) of the hyo- 

 mandibular. 



The interorbital septum is thin and bony. At the back of the 

 orbit is the alisphenoid (No. 17 of Erdl), in front of this the 

 orbitosphenoid (No. 18), and below and partially betw^een them 

 is a fair-sized basisphenoid (No. 16a). In front of the orbito- 

 sphenoid is a curious bone (No. 6) which forms the most anterior 

 part of the interorbital septum, and is united laterally by jagged 

 sutures with the upper edge of the ectopterygoid and the 

 postero-superior edge of the palatine. There seems to be no 

 alternative but to regard this bone as the two prefrontals fused 

 in the median plane. The crania] cavity is continued into the 

 upper part of this bone, and divides anteriorly into two passages 

 transmitting the stalks of the right and left olfactory lobes of 

 the brain. 



The connection between the hyopalatine arch and the cranium 

 is of a far more intimate and rigid nature than in any other of 

 the Mormyridee examined : there can be no possibility of move- 

 ment of the hyopalatine arch. The axis of the hyomandibular is 

 drawn forward until it is nearly horizontal. The parasphenoid 

 is short, broad, and nearly flat (No. 16 in Erdl's lower figures), 

 and its anterior part is underlaid by the broad tliin end of the 

 bone No. 5, which I take to include the vomer, the endosteal 

 mesethmoidt, the two palatines, and the two entoptery golds, 

 fused together. This bone has no teeth ; neither has the para- 

 sphenoid. The metapterygoid (No. 22) lies nearly horizontal in 

 the floor of the orbit, above the lateral expansion of the para- 

 sphenoid. There is no recognizable symplectic. 



The posterior extremity of the epiotic ridge (No. 10) is in 

 intimate ligamentous relation with the stout upper end of the 

 supraclavicle (No. 36). The post-temporal (No. 36*) is quite a 

 small bone, of which none of the three usual limbs (epiotic, 

 opisthotic, and supratemporal) can be recoguized. It lies 

 immediately external to the junction of the supraclavicle with 

 the epiotic. 



t The ectosteal mesethmoid (No. 7) is readily separable from this. The 

 closer union of the endosteal mesethmoid with the vomer than with the 

 ectosteal mesethmoid is paralleled in Megalops. 



