44 ON THE APPEXDICES GEXITALKS (CLASPERSl IX THE SELACHIANS. 



projects, bent at its rise, but otherwise straight, cylindrical, and rounded posteriorly. It is necessary 

 in order to get a view of this piece T 3 , and to isolate it together with Tv, to cut away part of the 

 outer lamella of the ventral marginal cartilage. 



The muscular system. The M. adductor shows no deviations from the common type; the 

 M. extensor, on the contrary, shows the peculiarity of being divided into two independent muscles 

 (com p. Torpedo), an inner (medial) one, and an outer (lateral) one, bordering on each other, and both 

 originating from the basale; the inner or foremost one arises rather far forward on the basale alone, 

 runs, like the -1/. extensor in the Greenland Shark, across the appendix-knee, covering as a thin plate 

 part of the dorsal side of the M. dilatator, and ends quite posteriorly, at the terminal part. The outer 

 or hindmost extensor arises behind the foregoing one, not from the basale only, but also from the 

 pieces b T , b 2 , # 3 , and it is attached to the appendix-stem immediately behind the knee . 



The M. dilatator, as is commonly the case, encompasses the appendix-stem from the dorsal 

 marginal cartilage to the ventral one; the lateral part of it arises forward on the ventral side of the 

 basale and the short pieces following this latter (comp. the Rays); behind its chief portion is attached 

 to the ventral covering piece v. 



Of the M. compressor the bagshaped part is rather short, and does not nearly reach to the 

 pelvis, but otherwise it agrees with the one found in other Sharks. The outer lip-muscle is very 

 powerful as in the other Sharks with a short Rv, and is attached posteriorly chiefly in the aponeurotic 

 covering of the piece Tv. 



The secreting part of the glandular bag shows in its foremost part the same relations as 

 in the other Sharks; but in the part which is situated in the shaft itself, a large glandular body (see 

 fig. 13 and 14) has been developed on the ventral side. The presence of this gland may already 

 be guessed by the peculiar exterior of the appendix-shaft; its proximal part shows, when seen from 

 the ventral side, a peculiar convexity, by which the organ gets a contour not unlike that of a human 

 leg with a large calf. The glandular body reaches before quite to the beginning of the bagshaped 

 part, that is to say, much farther than the appendix-slit itself, so that it is necessary to cut Tip some 

 way (see fig. 13) in order to get a view of the foremost end; it is a little tapering behind, and reaches 

 to the terminal part. A slight, longitudinal furrow is found on the free (dorsal) surface about the 

 middle, and on the edges of this furrow are situated two series of large glandular outlets; a great 

 number of similar outlets are also found laterally of the furrow, in jDretty irregular groups; to the 

 medial side of the furrow are also some such openings, but apparently in much smaller number. When 

 the gland is pressed an abundance of mucus will appear as stoppers in the said outlets. The glan- 

 dular body is composed of dichotomously branched tubes, quite similar to those found in the Rays, 

 and with quite similar large secreting cells; but they are here grouped in a somewhat different 

 manner 'as a consequence of the outlets of the gathering ducts being spread on a much greater space. 

 The glandular body in Rhina furthermore deviates from that of the Rays by its ventral position in 

 the shaft ! ), and by not having the special muscular coat developed as in those; the part of the M. compressor 

 situated at the gland will very likely be able to act in a similar way, possibly only with less force, in R/iiua. 



' In Torpedo, Narcine, Rhiuobatus and Trygon the dorsal glandular body of the bag is continued throughout the 

 shaft with the same structure as in the bag, but reduced in bulk, and situated along the ventral marginal cartilage. If in 

 one of those Ray-forms the part of the gland situated in the bag be supposed absent, and the part in the shaft displaced 



