74 ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 



as it has no antagonist, the resistance of the surrounding skin, and, I think, also the pressure of the 

 abdominal muscles over the base of the pouch, must be regarded as the cause why the organ folds 

 back and is hidden in the pouch, when the muscle m is relaxed. The way in which this muscle is 

 attached, has been described more in detail by v. Davidoff (I.e. p. 479). 



Callorhynchus antarcticus Lacep. 



The appendices have been briefly mentioned by Dumeril (I.e. p. 6S1) as follows: «Ceux des 



Callorhynques consistent en des prolongements cutanes, enroules de maniere a former uue paire 



de cylindres creux et irreguliers que soutiennent des cartilages flexibles ; the foremost pair of organs, 

 which are enclosed in the pouch, and have here a far more complicated structure than in Chimcera, 

 have been more particularly described. The same organs have later been mentioned, though still 

 rather briefly, by T. Jeffery Parker, in a kind of preliminary note 1 ), in which is found the rather 

 bold hypothesis, that these anterior appendages* in Callorhynchus are representing a middle pair of 

 limbs , they being understood as serially homologous with the real appendices; thus Callorhynchus 

 (and the Chinucru- in general) should (but to be sure only in the males!) show the remains of a hexa- 

 pod stage . The real appendices ( posterior claspers ) are only mentioned with a few words to the effect 

 that they correspond to those in the Plagiostomes, as they occur in the same position, have the 

 form of a plate rolled longitudinally into a tube, and are supported by a prolongation of the basir 

 pterygium». 



In a specimen (in the museum in Copenhagen) of a length of abt 70*™ I find the following 

 measures: 



The length of the (real) appendix from the fore edge of the cloaca 8,5° 



The length of the terminal part 5 cm 



The breadth across the base of the shaft i,7 c 



- middle of the terminal part 0,8 — 0,9° 



As to the habitus the appendix at a first glance reminds more of that in the Sharks than of 

 that in Chiuncm; but a closer examination shows a very near relation to the latter; it is only the 

 terminal part not being split into branches, that causes the apparent resemblance to the Sharks; the 

 shaft corresponds in shape quite to that in Chimcera, and is, as in this latter, covered with a thin, 

 naked skin, through which the extension and form of the muscles may be distinctly discerned; 

 on the terminal part there are, as in Chimczra, no muscles at all; but here the skin is every where 

 thin, and is lying immediately over the skeleton, so that a reliable view may be got of the 

 structure of this skeleton unfortunately I could not skeletonize the only male specimen of the 



museum. The terminal part is somewhat dorso-ventrally flattened with rather parallel sides, only 

 a little tapering towards the rounded end. 



On the dorsal side the appendix-slit rnus as a narrow slit, beginning, as in Chimcrra, with a 

 rather large opening at the base, close to the abdomen; this hole* is supported by skeleton to the 

 same extent as in Chi 111 a- ret; from here the slit runs in a curve through the shaft into the terminal 



'1 Notes from the Otago University Museum, VIII On the Claspers of Callorhynchus. Nature, vol.33, 1S86. p. 635. 



-cm 



-.cm 



