ORAL CIRRI OF SILUROIDS AND ORIGIN' OP THE HEAD IN VERTEBRATES. 17 



The former turns down outside the mentomeckelian process, while the 

 R. mentalis continues on above it and passing forward horizontally, 

 parallel to the R. maudibularis externus, divides into small twigs 

 which supply the posterior face of the mental tentacle. 



An Ophthalmicus profundus is only represented by certain fibres 

 running in the course of the Ramus ophth. superficialis of the Facial. 



Sensory Tentacular Nerves of Myxine (Fig. 11). 



For purposes of comparison aud in view of the object of this paper, 

 I venture to give a figure of the terminal distribution of the sensory 

 branches of the Trigeminus in Myxine, with some description, though 

 I have only one point to add to the almost perfect account given by 

 Johannes Midler in his classical memoir. 



In the figure the anterior part of the irregular nasal skeleton is 

 shown, and supplying the skin in this region are several twigs belonging 

 to one of the branches of the Ophthalmicus profundus (R. o, p.), the 

 upper terminal branch of the first branch of the Trigeminus of Miiller, 

 5'" in his figures. One twig also proceeds to the premaxillary tentacle 

 (shown in my figure with an asterisk). 



The branch termed Ramus premaxillaris (R. pmx. in the figure) is 

 Midler's "lower stouter branch of the first branch of the Trigeminus, 

 5""." It runs alongside the premaxillary piece, the " vordere knocherne 

 Stiitze der Schnauze," and, after giving off motor branches, supplies 

 the first or premaxillary tentacle. 



The above two branches form the " upper anterior branch of the 

 Trigeminus " and both are said to run above the optic nerve in 

 Bdellostoma. They are by most authors termed ophthalmic branches, 

 And I have kept that name in my preliminary communication. 



The remaining branches belong to the " anterior lower branch " of 

 Miiller. The maxillary nerve (R. mx.) is his branch 6' and the 

 ■coronoid (R. cor.) is his branch 6'". They supply the maxillary and 

 coronoid tentacles. 



My Ramus mandibularis (R.md.) corresponds to the "deeper finer 

 branch, 6", of the anterior lower branch." Only the sensory part is 

 shown in the figure. It divides into a Ramus mentalis (R. ment.) 

 supplying the fourth or mental tentacle, and a Ramus submandibularis 

 (R. subm.), not specially mentioned by Miiller, which supplies the skin 



