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on the surface of the mylohyoid muscle, presumably by means of a fibrous inscription but the 

 precise details of their insertion I could not determine in this foetus. Carte and MacAlister 

 describe a peculiar fibrous structure in connection with the mylohyoid and as their description 

 is somewhat obscure to me I give it literally: "Occupying the inferior or superficial part of 

 the interspace between the rami of the lower jaw in the anterior part of the middle line was 

 a condensed fibrous expansion, which extended forwards as far. as the symphysis, and was bifur- 

 cated posteriorly at the middle point of the lower jaw, giving attachment to the following muscle 

 (mylohyoid)." In a foetus of Megaptera versabilis of Mr. Andrews's collection which I dissected 

 with a view of gaining a better understanding of the musculature of the ventral pouch, a fibrous 

 structure somewhat resembling the foregoing was present. In the midline immediately behind 

 the symphysis mandibularum a sagittal ridge projects from the surface of the skin with a length 

 of something over 1.5 cm. This is caused by a local thickening of the derma. Caudad its sur- 

 face relief ends abruptly, but on dissection it is found to be prolonged by two fibrous strands 

 on the surface of the mylohyoid, parallel to and at a distance of about 1 cm. from the lower 

 margins of the mandibles, extending for somewhat more than a third of the length of the jaw. 

 The whole tendinous structure has then the shape of a Y, the stem at the symphysis and the 

 arms stretching caudad roughly parallel to the mandibular rami. It thus would have a general 

 resemblance to the structure described by Carte and MacAlister, if they could be understood as 

 meaning that it terminates, not bifurcates, opposite the middle of the ramus. That this was 

 their intention is, I think, probable from their description of the mylohyoid muscle, of which 

 only the anterior portion is given as arising from the fibrous structure, the remainder having the 

 usual origin from the mandible. It remains to question whether this fibrous structure actually 

 replaces the mandible in part as the origin of the mylohyoid or serves some other purpose. In 

 the fcetus of B. borealis I thought I could follow the mylohyoid to the jaw in its whole length. 

 In that of Megaptera this was certainly the case, and the fibrous arcade received only fasciculi 

 of the ventral panniculus, which were thus attached to the ectal surface of the mylohyoid by a 

 tendinous inscription. The contraction of this part of the panniculus would therefore seem to 

 serve to deepen the oral cavity by pulling down the floor of the alveolingual region. Not all 

 of the fasciculi of the ventral panniculus had this insertion, however, for some were prolonged 

 beyond the inscription and passing over the border of the mandible were lost in the substance 

 of the lower lip. 



Caudal to the intermandibular region the ventral- panniculus ascends upon the sterno- 

 mandibularis under cover of the overlying fasciculi of the dorsal panniculus. Its fasciculi are 

 inserted into the caudal portion of the lower lip and into the derma of the subocular furrow 

 that prolongs the vestible, and more caudally still reach the malar bone and the zygomatic 

 process of the squamosal. In the pectoral region they cross the axilla to reach the ventral 

 aponeurosis of the flipper, here joining the pectoralis, and caudal to the flipper they reach the 

 lateral raphe which unites them to the dorsal division. 



The innervation of the panniculus carnosus falls into two districts. Behind and at the 

 shoulder it is supplied by a pannicular or lateral thoracic nerve, the lateral cutaneous of English 

 authors, 1 which runs caudad beneath the lateral raphe distributing branches to both the dorsal 



1 Wilson, J. T. The innorvation of axillary muscular arches in man, with remarks on their homology. Jour. Anat. and Phys., 

 Vol. XXII, 1888. Further observations on the innervation of axillary muscles in man. Jour. Anat. and Phys., Vol. XXIV, 1889. 

 Birmingham, A/ Homology and innervation of the Achselbogen and Pectoralis quartus and the nature of the lateral cutaneous nerve 

 of the thorax. Jour. Anat. and Phys., Vol. XXIII, 1889. 



