424 



HARRIS HAWTHORXE WILDER ON 



. ■ i'3 ><y'-''i 



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 mandihulo-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 vevA' 

 large individuals, under the most favorable conditions as to preservation, has led me to 

 modify .somewhat the account given by Huxley, and to sub.stitute the interpretation 



graphically given in tlie accompany- 

 ing figure (fig. 22). The distal end 

 of the ceratohyal is traversed by a 

 deep groove in which runs the tendon 

 of the digastric muscle, and which 

 forms an oviter and an inner lip. 

 At the posterior end of the inner lip 

 there is developed a rather promi- 

 nent process. There are two distinct 

 mandibulo-hyoid ligaments, external 

 and internal, the one from the outer 

 lip of the digastric groove to the 

 lower corner of the angular pi'ocess, 

 and the other from the inner lip of 

 the groove and from its process to 

 the angular process just above the 

 attachment of the other. The hyo- 

 suspensorial ligament is a narrow but 

 very strong and distinct baud 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-suspeusorial " 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 cau 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 





Fig. 22. Relations of suspeasorium, jaw and hyoid, taken from 

 the right side. X 3. Lig. hyo-sus., ligamentum hyo-.suspenso- 

 riale ; lig. md.-liy. extern., ligamentum mandibulo-hyoidetun 

 externum; lig. md.-hy. intern., ligainentiun mandibulo-liyoideum 

 internum ; membrane, that between .skull and ceratohyal, fonu- 

 ing posteriorly a thickened band, extending between operculum 

 and ceratohyal. 



