258 



Its mesial edge abuts against, and slightly overlaps dorsally, the 

 lateral edge of the ethmoid, and ventral to that bone it abuts against 

 and overlaps ventrally the projecting rostrum of the chondrocranium, 

 the premaxillary here extending to the middle line and abutting 

 against the corresponding portion of its fellow of the opposite side. 

 This all appears in the descriptions and figures of the fish in one or 

 the other of the several well-known works upon the subject. 



The anterior edge of the premaxillary is furnished with a single 

 row of strong teeth. In one 30-cm specimen, which is the size I 

 have more particulary studied, there were seven of these teeth on one 

 side of the head and eight on the other, while in two other specimens 

 there where six teeth on each side. These teeth extend from the 

 mesial edge of the premaxillary bone of either side laterally to a 

 point directly anterior to pore 4 infraorbital of my descriptions of 

 the lateral canals of the fish (No. 4). As this pore no. 4 lies at a 



/^ , J -— ^ 



^\x 



PS 



PRr — -' Ecp 



-- ENP 



Fig. 1. Ventral view of the roof of the mouth cavity of Polypterus bichir, the 

 breathing-valve bones removed on both sides, and the maxillary, ectopterygoid, and ento- 

 pterygoid bones also removed on the left hand side. 



Iudex Letters. 

 AUP autopalatine. ECP ectopterygoid. ENP entopterygoid. ic^ sixth tube of 

 infraorbital lateral canal, ioc infraorbital lateral canal. ßlX so-called maxillary bone. 

 PMX premaxillary. pq palato-quadrate cartilage. PRE prefrontal, or antorbital ossification. 

 PS parasphenoid. VO so-called vomer, or breathing-valve bone. 



