1918] Davidso}) : The Musculature of HeptcnicJi us macuhitus 157 



ventral fibers are continuous with the dorsal part of the correspond- 

 ing muscle. They are attached to and held in place by the ventral 

 extrabranchial cartilages. The remaining part, which is anterior, 

 is inserted along the posterior edge of the ceratobranchial from the 

 epibranchial to the hypobrancliial segments. The first to the fifth pass 

 through the first five of the coracobranchiales muscles as described 

 below. The sixth interbranchial passes between the sixth and seventh 

 coracobranchiales. 



4. Trapezius {tr., fig. 1). The trapezius lies between the dorsal 

 longitudinal muscles and the dorsal constrictors, and is partly covered 

 by the latter. It arises from the fascia of the dorsal longitudinal 

 muscles, runs ventrally and posteriorly, and is inserted in two parts. 

 The ventral part, the origin of which is anterior, is inserted on the 

 epibranchial segment of the degenerate seventh branchial arch. The 

 remainder of the fibers have the same direction and are inserted 

 anteriorly on the pectoral girdle along most of the scapular part. The 

 trapezius raises the shoulder girdle and draws it forward. 



5. Levator lahialis superioris {Us., fig. 1). Vetter (1874, p. 448) 

 classifies this muscle in Acanthias vulgaris \vith the adductors, but 

 Marion (1905, p. 21 ) basing his judgment on Tetter's description places 

 it with the constrictors. In Heptanchus civereus, according to Vetter, 

 this muscle is absent. In Acanthias (Marion, 1905, p. 21 and Vetter, 

 1874, p. 420) there is a single pair of muscles, while in the skate (Ties- 

 ing, 1896, p. 85) the muscle is differentiated into four or five parts. 

 In Heptanchus maculatus the levator lahialis superioris includes two 

 distinct parts. The first corresponds to the first levator lahialis of the 

 skate or to the whole muscle as described for Acanthias, although the 

 two are not the same in origin. It is a small somewhat flattened band 

 having its origin on the inner side of the ant orbital process (a.pr.). 

 Its fibers run posteriorly and outward, cross the angle of the jaws, and 

 continue as a fibrous band of tissue which separates the dorsal and 

 ventral parts of the adductor mandibulae. The second probably cor- 

 responds to the second muscle as described for Raia by Marion (1905, 

 p. 22). Its origin is on the cranium just anterior to the preorbital 

 process, and in the region of the nasal capsule, by a wide band of 

 rather soft tendinous tissue. This continues posteriorly below the 

 eye where it joins similar tissue which surrounds the eye and then 

 crosses the adductor mandibulae. At its posterior end this tendon 

 passes inward and by a short muscular part, is inserted on the quad- 

 rate and mandible at the place of their union. 



