38 



ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 



fore the terminal part, is seen a small opening (/ in the fig. 10 in the text) of a length of i 1 2 cm ; this 

 opening leads into a deep, pocketlike invagination of the skin, lined with a soft continuation of this, 

 similar to a mucous membrane. On the dorsal side of the terminal part, at the lateral base, a polished 

 skeletal piece projects uncovered by the skin and like a thorn (T). The terminal part is easily bent 

 ventrallv; if bent in that way, the thorn, as in many other Sharks, will rise mechanically, and stand 

 out horizontally; it will immediately lie down again, when the terminal part is let loose. A dermal 

 fold supported by the skeletal piece Td, is prolonged forward into the tube formed by the marginal 

 cartilao-es in such a manner, that this tube gets two outlets, one on each side of the lamella concerned; 

 but the appendix-slit proper is situated laterally of this piece (a/ in fig. 10). 



The skeleton. Between the basale and the skeleton of the 

 appendix is found (almost as in the Scylliidse) one very small piece 6 Z , 

 highest on the medial surface, and otherwise quite low, that is to say, 

 wedge-shaped; in connection with the distal end of the basale and the 

 proximal end of the appendix-stem it bears the hindmost ray, which at 

 the base is rather broad. The piece ft is pretty well developed, and, as 

 is usual in Sharks, connects the basale with the appendix-stem. 



The appendix-stem is very long, twice as long as the basale 

 + b s \ proximally it is only a little calcified (comp. Selackus), but else it 

 is firmlv calcified in the surface until the terminal part, where it forms 

 a very long style, reaching to the hindmost end of the terminal part; 

 this style for the hindmost two third parts is calcified in the surface; 

 its soft basal part is situated immediately under the above mentioned 

 pocket ■; the distal end of the Musculus dilatator passes into the firm, 

 fibrous ventral wall of this pocket, in such a manner that its aponeurosis 

 is firmly inserted in the perichondrium above the calcified part of the 

 style, as well as in the corresponding places of the two adjoining calci- 

 fied terminal pieces Td and Tv\ the soft part of the style and the joints 

 between the marginal cartilages and the two skeletal parts Td and Tv 

 will then act as a kind of articulation 1 ). 

 The marginal cartilages are very long, hard, and thick; forward they reach almost to the be- 

 ginning of the appendix-stem; the dorsal one reaches somewhat longer forward and also somewhat 

 further backward than the ventral one. In the greater part of their length the two cartilages are in 

 contact with their margins; proximally the dorsal one is covered a little by the ventral one, the 

 margin of the former being bent somewhat into the tube enclosed by both; behind, a little before the 

 terminal part, they separate, and leave between them a slit broadening distally. 

 The number of terminal pieces is four. 



'I'd and Tv are long, almost equally developed; their distal ends are not calcified, and do not 

 reach quite to the end of the style. To the inner dorsal edge of Td is attached a piece Td 2 , which 



Fig. 10. 



Laniita cornnbica. The hind- 

 most part of the right appen- 

 dix seen from the dorsal side; 

 considerably reduced. / the 

 opening of a pocketlike inva- 

 gination of the skin. Tv, a 

 dermal fold containing no ske- 

 letal piece. 



M If we should suppose a skeletal part to be developed in the ventral wall of this pocket, it would in all respects 

 be corresponding to the covering-piece v found in Rkina. 



