320 JOURNAL OF COMPARATIVE NEUROLOGY. 
shift its position ventrally to pass to the outer surface of the 
quadratum, it becomes farther separated from the ear capsule 
leaving a space in which the quadratum appears. The ventral 
(lateral) edge of the squamosum is thin where the bone rests 
upon the ear capsule, but becomes thicker as the bone leaves 
that structure, i. e. where the stilus articulates with it, becom- 
ing thinner again as the bone applies itself to the quadratum. 
Fig. 4. Larval Spelerpes bilineatus, 43 mm. long; c.—stilus columellae ; 
v, j-—vena jugularis; #. 7.—nervus jugularis; d@. m.—M. depressor 
mandibuli; s.-~Squamosum. 
In the interval between the squamosum and the ear capsule, 
two processes of the quadratum extend backward, (1) a bony 
process applied immediately to the inner surface of the squa- 
mosum, extending back to the level of the cephalic end of the 
cartilage upon the ventral edge of the squamosum, and (2) a 
short cartilaginous process lying between the bony process and 
the ear capsule. The latter seems to be a part of the (morpho- 
logically) basilar process of the quadratum and is very short. 
