452 Edward Phelps AUis jr., 



other fishes already referred to, the dorsal hone of the postorbital 

 series is a dermal postfrontal. 



Figs. 19, 20 and 21 show the canals and surface sense organs in 

 an adult Esox lucius, and fig, 22 shows the canal bones of the skull 

 and their related sensory organs. The position, in this latter figure, 

 of the posterior organ of the left supraorbital canal leaves some doubt 

 as to whether that canal anastomoses with the main infraorbital by 

 its terminal or penultimate tube. 



The squamosal has a post-preopercular portion that lodges an 

 organ innervated by a postfacial nerve. There is a single extrascapular 

 bone, and it lodges one organ of the main infraorbital line, and also 

 the one organ of the supratemporal canal. The suprascapular is not 

 traversed by the main infraorbital canal, the bone lying internal to 

 a groove in the dermis that looks like a large and elongated primary 

 pore but is in reality a break in the canal, between its extrascapular 

 and supraclavicular sections. The suprascapular organ not having 

 developed, the related latero-sensory ossicle is also wanting. The post- 

 frontal bone, instead of being postorbital in position, has approximately 

 the position of the corresponding bone in Amia. 



The parietal is distinctly grooved beneath the strongly developed 

 middle head line to pit organs. 



Thei'e is a small so-called supraorbital bone which has no relations 

 whatever to the lateral canals. 



Salmo namaycush. Figs. 24, 25 and 26 show the pores of the latero- 

 sensory canals and the lines of surface organs on the head of one specimen 

 of this fish, and fig. 23 shows the related bones of another specimen. The 

 drawings used for these figures were made in 1887—88, and the 

 positions of the organs in the canals was not determined. 



There is, in this fish, and also in Salmo fontinalis, of which I 

 also have sketches, a well developed ethmoidal commissure of pit organs, 

 and also well developed anterior and middle head lines of the same 

 organs. The anterior head line extends backward until it meets the 

 middle head line, recalling, in general appearance, the arrangement 

 shown by (îole [25] in Ohimaera, where the supraorbital canal meets 

 and anastomoses with the supratemporal canal. But these two arrange- 



