ON THE APPENDICES GENITALES iCl.ASPERS) IN THE SELACHIANS. 47 



the ventral side of the end of the marginal cartilage Rv (on the dorsal side the corresponding spot 

 is seen protruding into the appendix-slit, at * in fig. 18). 



The descriptions of different Sharks given in the preceding section will have shown that the 

 common tvpe in the skeleton is clearly conspicuous; the single secondary skeletal pieces may vary 

 pretty much, as to their form, but their homologies are easily and surely demonstrated. Although 

 the mentioned species of Sharks cannot be said completely to represent the Sharks upon the whole, 

 yet they belong to so many different families that we may be justified in coming to the conclusion 

 that the skeletal structure of the appendix is in the Sharks rather simple and easily explained. This, 

 however, can in no way be said of the Rays in general; here, especially in the genus Raja, 

 may be found particularly complicated structures varying to a high degree even from species to 

 species; and as the Raja - species are those that have been especially examined by earlier authors, it 

 will easilv be understood that so few general results have hitherto been obtained. If, however, by 

 means of the Sharks we have got a clear understanding of the characteristic common features, it will 

 not be so verv difficult to point out these features also in the Raja-. It is, however, an obvious suppo- 

 sition that other forms of Rays than Raja will approach more nearly to the Sharks, and such forms 

 will most likely have to be sought among the shark-like Rays, as Rrisf/s, Rhinobatus , Torpedo, etc. 

 Throueh the kindness of Professor L tit ken I have from our museum obtained the material of the 

 two last-named genera, and of Torpedo I have also got some pairs of veutrals from Napoli. 



Batoidei. 



Torpedinidce. 

 Torpedo marmorata Risso. 



(PI. Ill, fig. 2S-31.) 



The appendix, like the whole fish, is naked, flattened, with tolerably parallel sides, the termi- 

 nal part oval, distinctly marked off from the shaft by a slight constriction. The appendix-slit runs 

 on the dorsal side quite straight, nearest to the lateral edge until the hindmost half of the terminal 

 part where it suddenly bends to the medial side, and with a curve reaches to the end. On either edge 

 of the terminal part is seen a lengthened slit, posteriorly widening somewhat like a buttonhole; either 

 slit leads into a blind, pocket-like bag, inside the later mentioned covering piece v 1 ). None of the 

 enclosed skeletal pieces are naked. 



In a specimen of the length of 29 cm , a breadth of I7 cm the following measures are found for 

 the appendix: 



!) Petri 1. c. pi. XVI, fig. 4 gives a — neither good nor exact — figure of the appendix, seen from the dorsal side. 



