I20 ALUS. [Vol. XVIII. 



lodges the anterior end of the utriculus. The ventral portion of 

 the line lies external to the eye-muscle canal. That part of the 

 branchial chamber that lies opposite the dorsal part of the line 

 may, accordingly, serve for the transmission of vibrations to the 

 ear, as Sagemehl claims for the corresponding part of the branch- 

 ial chamber in Atnia and other fishes (No, 64, p. 208). It is im- 

 portant, however, to note that there is in Scomber no true bulla 

 acustica nor bulla lagena, and that, excepting in the narrow^ line 

 above described, which lies mainly in front of and below the ear, 

 the branchial chamber is everywhere separated from the ear by 

 muscles or other tissues. 



2. Basal Line. 



The basal line (Figs. 29 to 34) contains five pieces, the anterior 

 and posterior of which are detached from the other three which 

 together form a single piece. The anterior piece is the basihyal ; 

 the other four are the basibranchials. The anterior basibranchial 

 is sometimes found in two separate parts or pieces, as will be de- 

 scribed below. 



The Basihyal (BH) is a lanceolate piece lying in the tongue 

 of the fish. Its dorsal surface is flat, its ventral surface convex. 

 The anterior third or two fifths of the piece is of cartilage. Its 

 posterior end, more or less rounded in different specimens, is not 

 capped with cartilage. Its hind edge is slightly thickened and 

 rests upon the dorsal edges of the distal ends of the bodies of 

 the hypohyals and upon the adjoining and corresponding edges 

 of the mesial processes of those elements. It overlaps, consid- 

 erably, the anterior end of the first basibranchial. It is firmly 

 bound by fibrous tissues to the hypohyals, the tissues arising 

 mainly from the lateral edges and ventral surface of the basihyal, 

 and being inserted on the middle portion of the lateral surface of 

 the distal end of the hypohyal of either side. These tissues form 

 the ventral portion and the base of the tongue of the fish. 



The First Basibranchial (BB'^) occupies about one quarter 

 of the length of the middle, united portion of the basal line. Its 

 anterior end is capped with cartilage, and its hind end united by 

 synchondrosis with the second element of the line. From the hind 

 edge of its dorsal surface a wide splint process projects backward 



