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Show ANATOMY OF THE LEATHERY TURTLE. 295 The muscle can be separated into three strands. The most anterior is the part inserted upon the skull, and forms a very definite muscle that passes from the mid-line of the throat just internal to the middle cornu of the hyoid. The other two strands are thinner and less defined. All three parts form towards the mid-line of the throat a fairly continuous sheet, whose hinder part extends back beneath the clavicular portion of the deltoid to the clavicle. Coraco-hyoideus (text-figs. 58-60. 20).- Origin : from the antero-dorsal border of the coracoid about its middle. Insertion : upon the ventral surface of the body of the hyoid. In its course it passes dorsal to the clavicle. Corcico-ceratohyoideus (2 1 ).-This muscle was continuous with the longitudinal muscles of the oesophagus. ]STo origin from the coracoid was seen (it may have been missed). Insertion: into the ventral surface of the body and middle and posterior cornua of the hyoid. It is stated (Hoffmann, p. 82) that this muscle is peculiar to Chelone. Genio-hyoideus (22).-Origin: the anterior two-thirds of the inner surface of the mandible, just above the insertion of the mylohyoid. Insertion : upon the anterior border and ventral surface of the middle cornu of the hyoid. Cerato-maxillaris (23).-Origin: the tip of the middle cornu of the hyoid. Insertion : upon the inner surface of the angle of the jaw, just above the insertion of the squamoso-maxillaris. Ceratoglossus (24).-Origin: the ventral surface of the proximal end of the middle cornu of the hyoid. Insertion: into the tongue. Dorso-occipitis (text-fig. 55. 26).-Origin : by tendon from the ventral surface of the second dorso-lumbar vertebra. Insertion : by a narrow tendon to the base of the skull 3-5 cm. in front of the foramen magnum. A flattish muscle, lying just ventral to the roots of the brachial plexus. It passes dorsal to the outer end of the posterior cornu of the hyoid, and at this point forms a narrow tendon. In most Chelonia (Hoffmann, p. 83) this muscle appears to have a more extended origin, including usually several dorso-lumbar vertebrfe, as well as the ribs connected with them. In its insertion it resembles the dorso-occipitis of Chelys and Ghelemys. Collo-squamosus (text-fig. 55. 28).-Origin : from the lateral parts of vertebrfe n., in. Insertion : upon the squamosal close above the dilator tubfe. Longus colli (text-fig. 55. 29).-A complex mass of muscle covering the ventral surface of the cervical vertebrfe. Upon its surface are a number of half independent tendinous slips. The detailed origins and insertions of its various parts were not made out. There was no origin from the anterior ribs or nuchal plate such as seems to occur generally (Hoffmann, p. 84). |