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Show 294 MR. II. II. BURNE ON THE [Apr. 1 8, vertebrae iv., v. Insertion : the hinder margin of the parietal between the insertion of the testo-occipitis and the mid-line. This muscle usually takes origin from vertebrae m., iv., v. (Bronn's ‘ Thierreich,' Bd. vi. Abt. iii. p. 79.) Testo-cervicalis (text-fig. 55. 16).-This muscle can be separated into a superficial and a deep part (a) Superficial part.-Origin : the nuchal plate parallel to the anterior border of the scapular articulation. Insertion: the latero-dorsal parts of vertebras h i ., iv., v., vi. (b) Beep part.-Origin : the carapace along the median border of the scapular articulation. Insertion : dorsal surface of vertebrae v., VI., VII. The two parts of the muscle form a very powerful mass, clearly separable in front and at their origin, but fused posteriorly. The muscle does not agree very well with the description of any of the neck-muscles given by Hoffmann in Bronn's ‘ Thierreich,' but most nearly resembles the testo-cervicalis, especially that of Trionyx, which rises from the nuchal plate and is inserted upon the 7th vertebra. Transversalis cervicis (text-fig. 55. 17).-Origin: the lateral parts of vertebrae iv., v., vi., v i i . above the transverse processes. Insertion: basioccipital and posterior zygapophyses of vertebrae i., i i . This muscle is the most lateral of the strictly dorsal neck-muscles. In other Chelonians it seems (Hoffmann, p. 80) to rise further forward and not to be inserted upon the skull. Testo-cervicalis lateralis (text-fig. 55. 18).-Origin: by several fiat strands from the deep surface of the testo-capitis near its origin. Insertion: by a round tendon to the transverse process of vertebra n. in conjunction with part of the sphincter colli. Sphincter colli (text-fig. 55. 19).-A sheet of muscle that covers the front of the throat from the tip of the posterior cornu of the hyoid to the clavicle. It varies considerably in muscularity in different parts. At its anterior and posterior ends it is strongly muscular, but in its central parts almost entirely fibrous and quite thin. It is inserted along the sides of the cervical vertebrae from the n nd backwards and to the inner anterior border of the scapula. I can find no mention of the sphincter colli being attached to the scapula in other Chelonians. Mylo-hyoideus (19 a).-An anterior extension of the sphincter colli sheet. Insertion : into the whole length of the inner surface of the mandible, just ventral to the genio-hyoideus, and by a small separate slip into the squamosal in the middle of the orio-in of the squamoso-maxillaris. Capiti-plastralis (text-figs. 55 & 59. 38).-A sheet of muscle covering the ventral surface of the throat deep to the sphincter colli. Insertion : the outer end of the clavicle, the lateral parts of vertebrae n . , i i i ., iv., and by a separate and very definite slip into the inner surface of the squamosal, just dorsal to the dilator tubae. |
