884 ME. WALTER E. COLI-rNGE ON" THE SEIfSOET [Dec. 17, 



exact relations to the facial. A commissural connection between 

 the trigeminal and vagus is present in Cerafodus (cf. Sanders, 14), 

 in Lepidosiren (?) \ and between the facial and vagus in Proto- 

 pterus (cf. Pinkus, 13). The commissure does not join the ganglion 

 but the ramus vagi lateralis at its commencement slightly beyond 

 the ganglion, as in Ceratodus, after which it passes beneath the 

 muscles lying close to, and parallel with, the vertebral column (a 

 feature common to Lepidosiren also) at the side of the centra and 

 dorsal to the spinal nerves. It passes backwards to almost the end 

 of the whip-like prolongation of the tail, becoming smaller poste- 

 riorly. Fine branches pass off ventrallj'^ at intervals, the distance 

 varying from five to twelve millimetres — each branch making a 

 ventral cm-ve and passing dorsally again to the lateral canal, there 

 breaking up into a series of fine fibres. 



The remaining branches of the vagus are not concerned with 

 the sensory canal-system and call for no special mention. 



III. The Ampullaex Cajstals. 

 1. General Description. 



One of the most interesting features in Chimcera is the presence 

 of groups of Ampullary Canals. They were first described in this 

 fish by Leydig (12). 



There are in Chimcera five main groups on either side of the head, 

 which from their position and for reference may be termed 

 respectively : — 



1. The Occipital group, situated anterior to that portion of the 

 main canal which leads to the occipital commissure. 



2. The Median group, a series lying on either side of the mid- 

 dorsal line of the head. 



3. The posterior and, anterior Supra-orhital grotip, situated 

 below the supra-orbital branch of the main sensory canal of 

 the head. 



4. The posterior and anterior Suh-orhital group, situated below 

 and above, respectively, the sub-orbital branch of the main 

 canal of the head. 



5. The posterior and anterior Maxillo-mandihular group, 

 situated above the maxillo-mandibular branch of the main 

 canal of the head. 



The posterior and anterior groups of the supra- and sub-orbital 

 groups are often continuous and in some cases one or both were 

 absent, on either one or both sides of the head: in such cases there 

 were sUght difierences in the branchii)g of the nerve (<*/. 4) The 

 position of these canals is by no means so constant as in the 

 Elasmobranchs, and isolated lines or clusters are fi'equently fouud 

 in other positions than those noted above. They are always dis- 

 tinct from the sensory canal-system. 



^ From the examination I have made of Lepidosiren I could not positiTely 

 say whether this commissure arises from the trigeminal or facial, but, from its 

 position outside the cranial cavity, I think the former. 



