The Lateral Sensory System in the Muraenidae. 141 



tlieir adjoining- ends, of the snpratemporal cross-commissure and tlie 

 lireopei'ciilo-mandibular canal. The lateral canal of the body begins 

 at an opening in the posterior wall of this continuous transverse 

 canal, the opening- not lying- directly opposite the one by which the 

 main infraorbital communicates with the same canal. 



The main infraorbital canal, as thus defined, contains ten lateral 

 sensory organs, but there are only nine related primary tubes; no 

 indication whatever of a primary tube being found between the ninth 

 and tenth organs of the line. Six of the nine existing tubes open 

 on to the outer surface by a single pore, the other three ending 

 blindly without surface opening. 



Pore No. 1 infraorbital has been already described. Pore No. 2 

 lies ventro-lateral and slightly posterior to pore No. 1, on a level with 

 and immediately posterior to the dorso-mesial edge of the base of the 

 nasal tube. The maxillary labial furrow begins immediately posterior 

 to this pore, the pore lying on the outer end of a short tube which 

 fills the space between the anterior end of the furrow and the base 

 of the nasal tube. The tube leading inward from this pore, that is, 

 tube No. 2 of the line, is short and runs dorso-postero-mesially to the 

 canal. Immediately anterior to this tube the main canal is wholly or 

 partly encircled by a short and delicate tube of bone, both ends of 

 which are slightly prolonged by the fibro-cartilage peculiar to the fish. 

 The bone lodges the first sense organ of the line, and is apparently 

 tlie antorbital bone of the fish. 



Immediately posterior to tube No. 2 the infraorbital canal comes 

 into relation with the lachrymal bone, which it traverses, lying in 

 part on its external surface, and in part wholly or partly enclosed by 

 l)ridges of bone. . 



The lachrymal is a flat triangular bone, the longest edge of which 

 is presented ventrally and overlaps the outer surface of the so-called 

 maxillary bone of the fish. The lachrymal lodges three sense organs 

 of the infraorbital line, the 2°'^, 3^^^ ^^d 4th the organs lying in 

 those parts of the canal that are either completely, or almost com- 

 pletely enclosed by bridges of bone. The 4^^ organ was always com- 

 pletely so enclosed in all of my several adult specimens; and the 8''^ 



