A42 ALITS. [VoL. XIV. 
mal, or to that bone and the suborbital bones. In Chimaera, 
what seems to be this same line of organs is said by Cole 
(No. 10) to be a ventral division of the infraorbital part of the 
main lateral line, and to be innervated, as the dorsal part of the 
line is, by branches of the buccalis facialis; a special branch of 
the main nerve being differentiated for the innervation of the 
organs of the ventral line and those of the associated group of 
ampullae. In Polyodon, what seems to be the corresponding 
line is enclosed in a canal (No. 11, p. 512). Asall of the sense 
organs of the lateral canals, both in Polyodon and in Chimaera, 
are said to be partly enclosed in bone (No. 11, and No. 1, 
p. 496), it is to be presumed that the particular organs here 
under consideration are so enclosed. Bone thus being, pre- 
sumably, formed in these two fishes in connection with this 
line of organs, is it not highly probable, wholly apart from 
Klaatsch’s opinion of the scleroblastic character of the organs, 
that bone should be also formed in connection with it in certain 
other fishes, or other animals? And that the bone once so 
formed might still persist even after the disappearance of the 
organs to which it owed, primarily, its origin? The conditions 
found in Polypterus and in the Stegocephali and other reptiles 
seem to indicate that such is the case. 
In Trematosaurus braunit, the preopercular lateral canal 
begins, according to Baur (No. 5), in the prosquamosal, runs 
downward, and downward and forward, through that bone, and 
then enters the jugal, where it joins and becomes part of the 
suborbital part of the main infraorbital canal of the animal. 
The united canals then run forward through the jugal into the 
maxillary, and end near the anterior end of the latter bone. No 
mandibular canal is given by Baur, or in any way indicated, 
either in the descriptions or in the figure. Because of the 
canal that traverses it, the prosquamosal is said by Baur to be 
the homologue of the preoperculum of fishes. 
A bony connection is thus found established in Tremato- 
saurus between the preoperculum and the suborbital chain of 
bones; and it is traversed by a lateral canal, which connects 
the preopercular and suborbital canals. A similar canal is 
said by Pollard (No. 31, pp. 546, 548) to be found both in Coc- 
