165 



of its nerves with the other cranial nerves, it has so far 

 been found impossible to devise really satisfactory experi- 

 ments. F. S. Lee, the latest investigator of the function 

 of the lateral line organs, concludes that they are con- 

 nected with the sense of pressure or equilibration, and 

 even if this be not the case, there is some reason to doubt 

 whether the latter can be located in the semi-circular 

 canals as in higher vertebrates. 



The Lateral Canal {lat. c). — This canal, in part the 

 " lateral line " of systematists, is supported during the 

 greater part of its length by modified scales. Arrived at 

 the region of the shoulder girdle it tunnels through the 

 post-temporal, and then for a short distance has no bony 

 support. It now enters a chain of ossicles, undoubtedly 

 metamorphosed scales, called supratemporal ossicles or 

 extrascapulse. The last or most posterior supratemporal 

 is attached to the dorsal surface of the pterotic at the 

 region of the posterior depression shown in fig. 1, and is 

 larger than any of the others. It consists of 2 parts, one 

 running longitudinally in a curve for the " lateral line, ' 

 and the other transversely and somewhat forwards for the 

 terminal portion of the supratemporal canal. Whilst in 

 this ossicle the lateral canal on the ocular side anastomoses 

 with the posterior extiemity of the infraorbital canal, and 

 then turns abruptly upwards almost at right-angles, and 

 afterwards forwards, the latter or anterior portion of the 

 canal being called by some authors the supratemporal 

 oanal {s. t. c). The last supratemporal ossicle of the 

 Plaice therefore corresponds to the second, third and 

 fourth of the Cod fused together. In one Plaice examined 

 there were in all l-'i supratemporal ossicles on the ocular 

 side, as described by Traquair, but the recurrent portion 

 of the canal, usually ])iesenl a< its antei-ior extremity in 

 the adult (see figs. 23 and 29) was absent in this specimen. 



