128 Edward Phelps Allis jr., 



single sense organ, and then turns upward behind the eye. A primary 

 tube, the fifth of the line, arises from the canal at the hind end of 

 this second bone, and opens on the outer surface by a single pore 

 that lies postero-ventral to the eye. This second bone of the infra- 

 orbital chain is thus a simple suborbital ossicle. In position it would 

 seem to be the second and posterior one of two suborbital bones, and 

 comparison with .Myrus show that it is such a bone, the larger 

 anterior bone of the chain, in Ophicthys, being in fact the lachrymal 

 of the fish completely fused with an anterior suborbital bone. 



Having left the one independent suborbital bone of the fish, the 

 infraorbital canal turns upward at a right angle behind the eye, and 

 traverses three little ossicles, at the dorsal end of which it turns 

 sharply backward again, anastomosing, at the bend, with the hind 

 end of the supraorbital canal. The three little ossicles here traversed 

 thus hold the positions, as compared with Amia (No. 1) and Scomber 

 (No. 9), of two postorbitals and a postfrontal, and the canal, as it 

 traverses them, gives off two primary tubes, one between each two 

 of the three ossicles. No tube is given off at the dorsal end of the 

 dorsal ossicle. 



The ventral end of the lower postorbital ossicle is firmly attached 

 by tissue to the dorsal surface of the bone that forms the upper jaw 

 of the fish, the so-called maxillary, the suborbital bone being similarly 

 but less firmly attached to the same bone and also to the outer sur- 

 face pf the lower postorbital bone. The lachrymal lies along the 

 dorsal surface of the same so-called maxillary bone, but is much less 

 firmly attached to it. If the lower postorbital and the one suborbital 

 bones of the fish were to become completely anchylosed with, instead 

 of simply attached to, the underlying bone of the upper jaw, a bone 

 closely resembling the so-caUed maxillary of Polypterus would arise. 

 This will be later further discussed. 



On leaving the dorsal end of the postfrontal the main infraorbital 

 canal turns directly backward, anastomoses at the bend with the hind 

 end of the supraorbital canal, and then enters a canal in the com- 

 pletely anchylosed bones of this part of the skuU, the canal quite 

 undoubtedly lying at first between the frontal and squamosal bones, 



