The Anatomy of Chlamydoselachus 



395 



Text-figure 69. 

 Endoskeleton and musculature of male pelvic fins of 



Heptanchus maculatus. 

 A — Skeleton of male left pelvic fin in dorsal view. 



h.l and b.2, connecting segments; ha., basal piece; ba.p., basipter- 



ygium; he., beta cartilage: pi., pelvic girdle; ra., radial cartilages. 



After Davidson, 1918, Fig. 8. 



B — Musculature of male right pelvic fin in dorsal view. 



ad., adductor muscle; cp., compressor muscle; d!., dilator muscle; 



f.e., flexor externus; f.i., flexor internus; p!., pelvic girdle; ra., radial 



muscles; s.m., muscle of sac or pocket. 



After Davidson, 1918, Fig. 9. 



detail by Goodey (1910. 1, pp. 564-565) whose 



Figs. 20 and 21, pi. XLVI, are reproduced as 



my Figures 22 and 23, plate V, alongside Fig' 



ure 21 which shows the endoskeleton. The 



radial muscles {Ra., Figure 23, plate V) ex' 



hibit a division into bundles paralleling the 



radial cartilages. Concerning the ventral radial 



muscles Goodey says: ''On the ventral side 



there are the radial muscles Ra., which originate on the pelvic girdle close to the 



median line and extend outward to the horny fibers. Toward the anterior end the separate 



bundles have fused together, thus corresponding with the fusion of the radials above." 



The muscles of the clasper have been described in Heptanchus by Davidson (1918, 

 pp. 165-167 and Fig. 9). Davidson's figure of the musculature is here reproduced as 

 Text'figure 69b alongside his figure of the endoskeleton (Text-figure 69a). In both 

 Chlamydoselachus (Figures 22 and 23, plate V) and Heptanchus (Text-figure 69b), the 

 musculature of the myxopterygium is simple as compared with that of most elasmobranchs. 

 Few differences are found when Chlamydoselachus and Heptanchus are compared with 

 each other. As pointed out by Daniel (1934, p. 110), the principal difference is in the ad' 

 ductors. In Heptanchus the adductor (ad. in Text-figure 69b) is a long muscle; in Chlamy^ 

 doselachus it (A in Figure 22, plate V) is relatively broad and fan-shaped. Also, in 

 Heptanchus the external and internal flexors are united at their origins, while in Chlamy- 

 doselachus the point of origin of the external flexor is far removed from that of the 

 internal flexor. 



From a functional point of view, certain muscles of the myxopterygia or claspers 

 of Chlamydoselachus are described by Leigh-Sharpe (1926, p. 312) as follows: ''The 

 musculature is represented by the anteroflexor muscle, which anteroflexes the whole 

 clasper for intromission, and the erector muscle which in this case causes expansion of 

 the apical valves by pulling on a common tendon. The anteroflexor muscle is strongly 

 developed in this genus." These muscles are shown (p. 472) in Text-figure 115b, after 

 Leigh-Sharpe. 



