1895.] AlfD AMPITLLAET CAlfALS OF CHIM^EA. 887 



gradually becomes wider as it leaves the surface and finally ex- 

 pands into an ill-defined ampulla (PI. LIII. fig. 9, a); (2) a series 

 of tubes much smaller than number 1, all of which lead into a 

 common tube, considerably wider, from \shich numerous ampullae 

 are given off (PI. LIII. fig. 9, b) • and (3) a simple unbranched tube, 

 at the base of which are a series of well-defined ampullae (PL LIII. 

 fig. 9, c). 



It is possible that ampullary canals like numbers 1 and 2 may 

 yet be found in the Elasmobranchii : a careful investigation of the 

 system in the Batoidei is much to be desired. 



The minute structure is almost identical with that of the Elas- 

 mobranchii, the chief difference being, that in the sensory organ at 

 the base of the ampulla, in Chimcera, the epithelium-cells of the 

 " Centralplatte " form a concavity, in which rests the " cupula 

 terminalis" of Solger (PI. LIII. fig. 10) ; whereas in the Elasmo- 

 branchii these cells are arranged as a flat plate as shown in fig. 11. 

 Solger was the first to describe this difference. 



3. Innervation, 



The ampullary canals are all innervated by branches of the tri- 

 geminal \ the branches which innervate the sensory organs of the 

 sensory canal-system giving off branches to the ampullae, as shown 

 below : — 



Sriofand anterior Supra- 1 ^"PP^i'n j'''. <^°"^1 \''''?*''f^f ^^' ''^'°"' 

 orbital group. ] ophthalmicus superfieiahs (V.). 



Posterior and anterior Sub- f Supplied by the ramus buccalis and maxillaris 

 orbital group. [ superior (V.). 



' The ramus maxillaris inferior supplies these. 

 Where there are a few scattered ampullary 

 canals in the mandibular region, branches of the 

 ramus maadibularis (V.) innervate them. 



Posterior and anterior Maxillo- 

 mandibular group. 



IV. SUMMAET AJS^D CONCIiUSIOIT. 



1. In Chimcera the canals and branches persist as open grooves, 

 agreeing in this feature with the condition which obtains in the 

 Elasmobranchii ; variations, however, sometimes occur. 



2. Unlike the condition found in many Elasmobranchii, in 

 Chimcera there are no fine dendritic branches from either the 

 lateral or main canal, or from any of the branches of the latter. 



3. Ampullary canals are present, three distinct types being 

 found in different regions of the head. Their number, position, 

 and even structure is subject to much variation. TJiey are all 

 innervated by branches of the triyeminal nerve. 



4. The innervation of the sensory canals &c. proceeds from 



1 " It is worthy of note that all the groups of ampullae — superficial ophthalmic, 

 inner and outer buccal, hyoid and mandibular — are supplied by dorsal branches 

 of the facial" (Ewart, 6- p. 81), 



