54 



ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 



The whole appendix, as the ventral itself, is naked, somewhat latero-ventrally compressed, almost 

 triangnlar, when cut through, but with rounded edges; the broadest surface looks inward, and is in 

 contact with the base of the tail; the appendix-slit follows the more narrow dorsal side till the term- 

 inal part, where apparently it separates into two slits, surrounding a lengthened-oval, firm, and hard 

 part, covered bv the skin {Tv]\ in reality, however, only the inner one of these slits is a continuation 

 of the appendix-slit {(i/)\ the outer one (/') leads into a deep < pocket* ending far forward, and limited 

 by the terminal skeleton proper and the covering pieces to be mentioned later. Immediately before 

 the passing of the slit into the terminal part its inner (dorsal) lip forms a rather large, soft, pigment- 

 ed dermal fold, which, however, is not seen externally, being placed under the overlapping firm edge 

 of the outer lip, supported by the covering piece v. 



None of the skeletal parts protrude through the skin. 

 The skeleton. Between the short basale and the appendix- 

 stem are found two pieces, b^ and ho, of about equal length, but b^ is 

 much the broader, especially proximally, where it is of the same breadth 

 as the basale, and where on its dorsal edge it articulates with a very 

 long piece /y, which, without touching /^j, reaches to the appendix-stem, 

 and articulates with the dorsal side of this almost quite to the fore 

 end of the dorsal marginal cartilage, b^ bears the last ray, which prox- 

 imally for a long way is coalesced with the last but one which articu- 

 lates with the end of the basale; these two are by ligaments firmly 

 connected with the ventral marginal cartilage. The appendix-stem is 

 long and powerful, more than twice as long as the basale -f (5, + '^2; 

 its hindmost part (a little less than half the whole length) is uncalci- 

 fied as a strong, broad style reaching to or only a little past the end 

 of the terminal pieces. The marginal cartilages are both calcified, the 

 dorsal one most solidlj'; they reach about equally far forward, and 

 occupy almost the distal half of the stem above the style; behind the 

 dorsal marginal cartilage reaches a little farther than the ventral one; 

 the latter is concave on its outer surface, while the former is partly 

 rounded. 



The number of terminal pieces is two, only Td and 7?' being found. 



Td is a large, externally rounded plate of pointed-ovate contour, thickest at the medial edge 

 along the style, and laterally quite thin; the lateral edge is fineh' indented. T7> likewise is large, but 

 the inner siirface, towards the appendix-slit, is rounded, while the outer silrface is deeply hollow as a 

 trough, both edges of which are somewhat bent towards the concavity. The whole ventral side of 

 the terminal skeleton, as well as great part of the ventral marginal cartilage, is covered by two hard, 

 calcified, firmly connected covering pieces v and v^, to which the M. dilatator is attached, and which 

 correspond to the single v in the preceding genera of Rays (in Narcine, as we have seen, the proxi- 

 mal-lateral corner of v had alread}- been partly separated as an independent piece, to which in Trygon 

 the larger piece v^ must be taken to correspond). The larger lateral piece 7'i shows distally a rather 



Fig. 23. 



Trygon violacea. 

 The left appendage from the 

 dorsal side; reduced. /' the open- 

 ing of the lateral pocket. I', Td, 

 Tv the parts of the skin, in which 

 the skeletal parts, indicated with 

 the corresponding letters, are in- 

 closed. 



