798 ALLIS. 
EXPLANATION OF PLATE XXXIII. 
Fic. 47. The same as Fig. 46, but still deeper. The hyoid arches and sterno- 
hyoidei have been cut so as to leave only their anterior ends, and the clavicles 
and the heart and blood-vessels have been entirely removed, so as to expose the 
under surfaces of the branchial arches and basal line, with the nerves and muscles 
that lie upon them. X 1%. 
Fic. 48. The same as Fig. 47, showing the ventral surfaces of the fourth and 
fifth ceratobranchials of the right side of the head, and the muscles associated 
with them. X 2. 
Fic. 49. Dorsal view of the branchial and hyoid arches of the left side of the 
head. X 1%. 
Fic. 50. Ventral view of the branchial and hyoid arches of the right side of 
the head. X 1%. 
Fic. 51. Side view of the basal line. X 1%. 
