1895.] AND AMPULLAB.T CANALS OF CHIMERA. 879 



1876, mentions both the canals and cranial nerves in his paper on 

 the skull of the Holocephali. Solger (15) in 1881 published an 

 account of the development and minute structure of the canals ; 

 and later Garman (9) described and figured their distribution in 

 both Chimcera and Callorhynchus. 



It was originally my intention to describe at some length the 

 cranial nerves, but lack of better material has prevented me. In 

 the ordinary spirit-preserved material the nerves are not in a fit 

 condition for histological work, and it is only with difficulty that 

 the distribution of the smaller nerves can be traced. 



The material was purchased from the Zoological Station at 

 Naples out of funds granted by the Council of the Eoyal Society, 

 and I take this opportunity of expressing my thanks and acknow- 

 ledging the assistance they have given me. 



My thanks are due to Professor T. W. Bridge, M.A., for his 

 very kind assistance throughout the work, and to Mr. G. A. 

 Boulenger, F.E.S., for his kindness in permitting me to examine 

 the series of young Chimcera and Gallorhynchus in. the British 

 Museum collections. 



II. The Sensoex Canal-Sxstem. 



1. General Description. 



In. describing the canals and branches I have not adopted the 

 nomenclature of Garman (9), as they may be grouped into a similar 

 series as in other fishes, and further, such a nomenclature lends 

 itself better for purposes of comparison. I have given below, on 

 the left side the nomenclature used in this paper, and on the 

 right that used by Garman. 



Lateral Canal = Lateral Canal. 



Main Canal of the Head = The Cranial Canal (part). 

 The Occipital Commissure = Aural and Occipital Canals. 

 The Supra-orbital Branch = The Eostral Canal. 

 The Sub-orbital Branch = The Orbital and Sub-orbital Canals. 

 The MaxiUo-mandibular Branch = The Angular, Nasal, and Oral 



Canals. 



The lateral canal commences at the end of the long whip-like 

 tail on the lower edge of the muscles, and passes forwards as an 

 open groove to the region of the head, where it is continued as the 

 main canal of the head. This passes forwards forming the supra- 

 orbital branch and in the anterior region joins with the sub-orbital 

 and maxillary branches. Dor sally an occipital commissure is 

 given, off from the main canal, and ventrally the sub-orbital branch. 

 From the angle of the sub-orbital branch a short branch is given 

 off — possibly homologous with the operculo-mandibular branch of 

 Ganoids and Teleosts and the hyomandibular branch of Elasmo- 

 branchs — which divides into maxillary and mandibular branches ; 

 previous to this division there is a short backwardly directed 

 branch, the "jugular canal" of Garman. The maxillo-mandibular 



56* 



