ON THE APPENDICES GENITALIS (CLASPERS) IN THE SELACHIANS. 53 



along the other pieces, b z b. /;,, and next articulates with the appendix-stem b in a long joint, reaching 

 as far past the articulation of /; 4 , as the length of this piece b^ itself; it reaches quite to the dorsal 

 marginal cartilage. It is narrow and flat, distally a little bent. The appendix-skeleton is of a length 

 about equal to the basale + b t . . . b 4 , the stem is rather slender, and ends in a style of a similar 

 shape and nature as in Torpedo, only it is here relatively very short. The marginal cartilages are 

 very long; both of them begin almost at the same point forward, the ventral one, however, a little 

 before the dorsal one, and they end at the style in an inverse ratio, that is to say, the dorsal one 

 reaching a little farther backward. On the greater part of their external surface they are very closely 

 connected with the teeth-covered skin, so that they only with difficulty can be separated from it. The 

 distal part of the dorsal marginal cartilage is, quite as in Torpedo, ventrally hollowed in a trough- 

 like manner; this part is hard and firm, shining, while the other part is more soft, lamellar, lying 

 like a cover over the appendix-slit, and forward reaching to /?. The terminal part on the ventral side 

 is covered by a piece v, quite corresponding to that in Torpedo and Narcine\ the margins, however, 

 are without folds. 



The number of real terminal pieces is three. 



Td is very small, a little concave on its ventral side; Tv is larger, and bears on its lateral 

 edge a process directed forward; it is externally flatly rounded, internally towards the appendix-slit it 

 has a trough-like concavity. T, articulates with the hindmost lateral edge of Rv, and with the fore 

 end of Tv; proximally it is broadly ovate, and distally it tapers to a shining conical point, which, as 

 already mentioned, is uncovered by the skin. 



The muscular system is principally as in Torpedo; the J fuse, extensor, however, is single, 

 as in Narcine. The glandular bag occupies here, as in those two genera, the space between the distal 

 end of the basale and the proximal end of the appendix-stem, but laterally it spreads over the hind- 

 most rays in a similar manner as in Raja. 



The glandular body is very narrow, and does not anteriorly reach the end of the bag; 

 accordingly it fills the inner space of the bag to a far less extent than in the other Rays; it is pro- 

 longed as a thin, raised stripe, provided with a furrow and gland-pores as in Torpedo and Narcine, 

 throughout the length of the shaft till the terminal part. 



Trygonidce. 



Trygon violacea Bonap. 

 (PL III, fig. 38-40.1 



A specimen of a length of i m , a breadth of 44 cm shows the following measures 



The length of the whole appendix 9 cm 



- free part 6,5 



from the fore end of the slit to the hindmost point of the appendix 8' 



The length of the terminal part 4' 



The largest breadth at the base of the terminal part 1,5 



era 



«jcm 



<cm 



cm 



