1918] Davidson: The Musculature of Heptanehus maculatus 165 



be counted, although the anterior part here is not clearly divided. 

 They have their origin on the posterior side of the coracoid portion 

 of the pectoral girdle, on the pro-, meso-, and metapterygia and on 

 the cartilaginous fin-rays. Their direction is the same as in the dorsal 

 series and they are inserted in the connective tissue which is continuous 

 with the ventral dermal fin-rays. 



The pelvic fins are located ventrally, one on each side of the 

 external opening of the cloaca. In the female the musculature is 

 quite simple, consisting of a dorsal and ventral series of radials. In 

 the male the muscles of the clasper are quite complicated. Krall 

 (1908) described these muscles for Hexanchus. The muscles are 

 similar to those of Heptanehus, but the terminal cartilages described 

 have not been found in Heptanehus maculatus. This may be due to 

 the immaturity of the specimens studied. The naming of the muscles 

 was taken from Goodey (1910) and Huber (1901). 



In the female the dorsal radials of the pelvic fin number twenty- 

 four. Their origin is double, from the connective tissue of the ventral 

 body muscles and from the fin-skeleton. The direction of the muscles 

 is outward and posterior. They insert in the connective tissues as do 

 the radials of the pectoral fin. Ventrally there are twenty-six radials. 

 Their origin is on the girdle, in the connective tissue posterior to the 

 girdle, and on the entire cartilaginous skeleton. The insertion is the 

 same as in the dorsals. 



The radials of the pelvic fin of the male (fig. 9) are similar to 

 those of the female. Dorsally in a large specimen they numbered 

 twenty-one and ventrally twenty-three. Besides the usual dorsal 

 radials there is, in the male, a posterior mass of muscle having its 

 origin in the fascia of the ventral longitudinal muscles. This passes 

 almost directly posterior where it spreads out and is continuous with 

 the posterior dermal fin-rays which fold around the clasper. 



The musculature of the clasper includes six muscles, an adductor, 

 two flexors, a dilator, a compressor, and the sac muscle. In all the 

 origin is proximal and the insertion distal. 



Adductor (ad., fig. 9). The adduetov is a specialized part of the 

 ventral musculature of the pelvic fin. It has its origin on the posterior 

 border of the pelvic girdle and from the connective tissue posterior 

 to the girdle. The direction of the fibers is posterior and the insertion 

 is medial on the distal end of the basipterygium (see ha. p., fig. 8). 



Flexor externus (f.e.). The flexor externus has its origin along 

 the middle third of the inner edge of the basipterygium. Its course 



