260 DK. W. G. EIDEWOOD ON THE 



pair of intermuscular bones, and a pair o£ large ribs*, whicb are 

 attached to the upper ends of the clavicles. This half-vertebra is 

 not shown in figs. 6, 7, and 8, but a separate view of it is given 

 in fig. 11. Since both the ribs and the intermuscular bones slope 

 backward as well as outward, they appear in the figure shorter 

 than they really are. These ribs are shown at a in Hyrtl's pi. 2. 

 tig. 1 ; the bones marked h are the ribs of the next vertebra but 

 one, a fact which one would not gather from an examination of 

 his figure, nor from his description of them (p. 88) as " das erste 

 Eippenpaar." 



The opisthotic is fairly large, and extends forvpard to meet the 

 pro-otic, but above the junction of the opisthotic with the pro- 

 otic there is no subtemporal fossa. The posterior temporal 

 groove is not well marked, although in Arapaima and Osteo- 

 glossum there is a completely roofed posterior temporal fossa ; 

 the lateral temporal fossa is roofed over by the squamosal bone 

 to a greater extent than in Osteoglossum. The side view of the 

 skull shows a large foramen between the exoccipital and basi- 

 occipital, bounded mainly by the former bone ; it is apparently 

 the vagus foramen, much larger than usual. The postfrontal is 

 fairly large ; the prefrontal is of moderate size. These bones 

 are not sculptured, being covered by bones of the circumorbital 

 series. 



The cranial cavity extends forward through, and in front of, 

 the orbital region, so that the membranous interorbital septum 

 is reduced to a small tract between the alisphenoids and the 

 parasphenoid. The two alisphenoids meet along their ventral 

 edges in a median suture, and the hinder end of this suture meets 

 an upwardly directed process of the parasphenoid. The orbito- 

 sphenoid is a broad, imperfectly ossified sheet of cartilage, 

 U-shaped in section. It rests upon the parasphenoid, and is 

 united with the prefrontals anteriorly, with the alisphenoids 

 posteriorly, and with the frontals above. 



There appears to be no basisphenoid. The eye-muscle canal 

 does not open posteriorly. Neither the vomer nor the para- 

 sphenoid bears teeth. The parasphenoid divides posteriorly into 



* Although a pair of strong intermuscular bones pass from the occipital 

 half-vertebra to the upper ends of the clavicles in Chanos, they are not homo- 

 logous with the bones now under consideration, which arise lower down the 

 side of the half-centrum and are in serial order with the ribs. The resemblance 

 in the two cases is curious, but it is not one of homology. 



