424 HARRIS HAWTHORNE WILDER ON 
important morphological bearing that a description of it is worthy of special consideration. 
Huxley (74) was the first to describe carefully this region in Necturus, and according to 
this author there are three important ligaments in this region: (1) a mandibulo-hyoid 
between the angular process of the mandible and the distal end of the ceratohyal; (2) a 
hyo-suspensorial between this latter point and the quadrate; and (3) a suspensorio- 
stapedial, from the quadrate to the operculum. A series of dissections of several very 
large individuals, under the most favorable conditions as to preservation, has led me to 
modify somewhat the account given by Huxley, and to substitute the imterpretation 
graphically given in the accompany- 
The distal end 
of the ceratohyal is traversed by a 
ing figure (fig. 22). 
Soo deep groove in which runs the tendon 
of the digastric muscle, and which 
Membrane. 
Groove for 
tendon of ‘ 
Digastric Tauscle, ri 
forms an outer and an inner lip. 
At the posterior end of the inner lip 
there is developed a rather promi- 
nent process. There are two distinct 
Lig. md-hy 
extern, ff mandibulo-hyoid ligaments, external 
Lig. ma-hy and internal, the one from the outer 
intern. 
lip of the digastric groove to the 
Fig. 22. Relations of suspensorium, jaw and hyoid, taken from 
the right side. X 3. Lig. hyo-sus., ligamentum hyo-suspenso- lower corner of the angular proces: 
riale; lig. md.-hy. extern.,. ligamentum mandibulo-hyoideum and the other from the inner lip of 
externum ; lig. md.-hy. intern., ligamentum mandibulo-hyoideum the groove and from its process to 
internum ; membrane, that between skull and ceratohyal, form- ° 
the angular process just above the 
The hyo- 
suspensorial ligament is a narrow but 
ing posteriorly a thickened band, extending between operculum 
attachment of the other. 
and ceratohyal. 
very strong and distinct band extending between the middle of the inner lip of the 
digastric groove and the outer side of the quadrate bone. In spite of repeated careful 
dissections I could not find any definite “ stapedio-suspensorial ” ligament, but instead of 
this a rather soft and somewhat indefinite sheet of connective tissue extending along 
the entire inner lip of the ceratohyal and attached along a corresponding length of the 
skull, involving the operculum, a bit of the cartilaginous otic capsule, and a part of the 
quadrate. At its posterior edge its fibers become stronger and thicker, and thus resemble 
a hyo-stapedial ligament, but as this part is directly continuous with the remainder of the 
sheet and is by no means as definite as the other genuine ligaments, it can hardly be 
described as a definite part. This loose sheet of connective tissue, which, as a matter of 
fact, adheres very closely to the columellar process of the operculum, is undoubtedly the 
