316 JOURNAL OF COMPARATIVE NEUROLOGY. 
The following description of the relations in a Necturus of 
49.5 mm. length, based in part on a model of this stage (Fig. 1), 
will serve asa basis of comparison. The operculum at this 
stage is roughly oval in outline and slighly ridged along its long 
axis. At its cephalic end it is fused with the otic capsule, pro- 
jecting backward into the fenestra vestibuli. From the cephalic 
end a dense ligament passes cephalad and dorsad to the os 
squamosum at about its middle point. The bone forms a slight 
curve, the convexity looking upwards, and it lies upon the 
external semicircular canal of the otic capsule, extending down 
over the otic process of the quadrate and becoming closely 
connected with a bone lying upon the external surface of the 
quadratum, and which it partly covers. This bone’ I shall 
describe in another place. The squamoso-opercular ligament 
is attached to the under side of the squamosum where the bone 
passes from the ear capsule to cover the outer side of the pro- 
cessus oticus quadrati. At this stage the ‘‘stapedial’’ process 
of the squamosum present in the adult has just begun to de- 
velop. The ligament, in its course from the operculum to the 
squamosum, passes external (laterad) to the ramus jugularis 
facialis and the vena jugularis. The ramus jugularis passes out- 
ward and slightly backward, between the ligament and the vein 
to the dorsal edge of the former where it receives the ramus 
communicans glossopharyngei, which lies close to the ear cap- 
sule laterad to the vena jugularis. Beyond the point of the 
union with the ramus communicans, the jugular branch of the 
seventh passes outward, under the ventral edge of the squamo- 
sum to curve around the dorsal side of the otic division of the 
M. depressor mandibuli. The ramus mandibularis externus 
facialis from its ganglion which lies immediately outside the 
foramen for the facial nerve, in a depression just caudad of the 
1 This bone arises in Necturus as a separate ossification, whose lower end 
subsequeutly is fused with or becomes the ossification of the quadrate. In 
Desmognathus and Spelerpes the same bone lies farther back, projecting under 
the squamosum, and in the adult forms the process of the quadrate named for 
the purposes of this paper the subsquamosa! process. 
