426 Edward Phelps Allis jr., 



orbital ossification), that bone being the postfrontal of Jnge's de- 

 scriptions. Before reaching the hind edge of this bone it pierces the 

 dorsal layers of the bone, thus becoming, for a short distance, enti- 

 rely enclosed in it. Leaving this bone it enters the squamosal, in 

 which bone it connects with the preopercular canal, and leaving the 

 bone enters and traverses the suprascapular. The squamosal lodges 

 three sense organs, as in Ameiurus nebulosus, but these organs are, 

 according to my sketches, the 6 th., 7 th. and 8 th. of the main infraorbital 

 line, instead of the 7 th., 8th. and 9 th., as in both Ameiurus nebulosus 

 and A. melas. As in both the latter fishes, there is no supratemporal 

 canal, and, as in A. nebulosus, there is no separate extrascapular 

 bone, the lateral extrascapular here, as there, being fused with the 

 hind end of the squamosal. 



No parietal bone, similar to the one in A. nebulosus, could be 

 found in Silurus, nor was there any indication of a fusion of such a 

 bone either with the epiotic (exoccipitale) or with the supraoccipital. 

 On the top of the skull, at the place where Juge shows a parietal, 

 there is a defect in the bones rather than a separate bone, but I 

 should greatly doubt its being a parietal; that bone then either being 

 wanting in this fish, or being indistinguishably fused with some 

 other bone. 



In Silurus the relations of the frontal, squamosal, and sphenotic 

 (postorbital ossification) bones to each other and to the lateral canals 

 closely resemble those of those same bones in Amia. 



Auchenaspis. In a 5 cm specimen of this fish, according to 

 Pollard [60], the first two organs of the supraorbital canal are each 

 protected by "feeble bone" developed in its immediate neighbourhood, 

 and the two ossicles thus represented quite undoubtedly later fuse to 

 form a single nasal bone. The remaining three organs of the line 

 are said to be enclosed in the frontal. The canal anastomoses with 

 the main infraorbital by its 5th. or penultimate primary tube, the 

 terminal tube of the line being tube No. 6, and not No. 5, as Pollard 

 gives it. 



The first five organs of the main infraorbital line are said to be 

 each protected by what Pollard describes as a small "rudimentary" 



