ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 29 



nial origin accordingly is much more backward, at the distal end of the J/. adclitctor\ it is inserted as 

 usual, its aponeurosis being especialh- attached to Tv and Td\ the latter piece, «the hook>, is turned 

 (round its medial edge as the axis) out of its position in the spoon-shaped end of the former, when 

 the muscle is contracted during the dilation. 



The part of the J/, compressor wrapping the bag, is much distended, and consequenth- rather thin, 

 corresponding to the considerable extent of the bag anteriorly (see fig. 4 in the text). The part inserted 

 on the lateral surface of the appendix-stem, is \-ery small, reduced to a few bundles of fibres on the 

 proximal end of this part of the skeleton, which otherwise is almost quite enclosed by the M. dilatator. 

 The part, which as outer lip-muscle forms the lateral limit of the appendix-.slit, seems to me to 

 receive in its surface some fibres coming from the muscular layer originating from the lateral muscles 

 of the bod}-, but otherwise it originates as usual on the hindmost rays and on /?; it is inserted with 

 a kind of tendon in the above-mentioned membrane on T%\ and consequently it acts antagonistically 

 against the J/, dilatator^ and at the same time lays the spur Z,'). 



Spinax niger Bonap. 



(PI. I, fig. 12, 13. 1 



The very peculiar-looking appendages in this common Shark ha\-e singularly enough been 

 very little mentioned by earlier authors, and by many, also among the later, the)" are not mentioned 

 at all. Gunnerus^), in his description of the . Sort-Haa >, says: tthey (i.e. the two Alcmbra genitalia) 

 were supplied with some sharp bony spines, such as 1 have seen on the Membra of se^■eral Raws, 

 when the ends have been turned in.side out. > Kroyer-') says: ^At the end of the cojiulatory appen- 

 dages of the males are found three crooked thorns or horny claws, and a tapering dermal flap, which 

 behind projects a little over these claws. The claws are movable against each other, and form a kind 

 of prehensile organ. In the position of rest the}' are hidden between a j^air of small cartilaginous 

 plates, and the skin covering these plates.s This is the most complete, and also, I think, the most 

 correct description I ha\e seen-*). Dumerils) gives a drawing of the appendix, but with no explana- 

 tion whatever (nor in the text neither); the drawing is rather difficult to understand, neither is it 

 correct; thus the dermal flap mentioned b}- Kroyer appears in this figure as a thorn, althoiigh it is 



1) Petri (I.e.) designates this part of my M. compressor as M. levator (fig. 5, tnl), and attributes to it a dilating 

 effect, having allein die Aufgabe diesen (den Sporn) zu heben >, and thus he in this place speaks of two dilating muscles. 

 The incorrectness of this, hcwever, is easih- pointed out. Contrary- to Petri, Bloch upon the whole has a correct understanding 

 of the mobihty of the spur, speaking (I.e. p. 13) of < einen sehr sonderbaren Mec/ianistniis. Davon mir wenigstens in der 

 Anatomic kein ahnlicher bekandt ist >. Bloch has a chiefly correct description of the muscular sj-stem; he distinguishes between 

 three muscular portions, the first of which being the ventral ray-muscles, the second, which he compares to the < adductor 

 femoris > in man, is ni}- .'1/. addiicior, the third M. dilatator -(- my AI. extensor. He describes the glandular bag as a parti- 

 cular organ, to which he does not ascribe any muscular walls, as he supposes that the other (2) muscles expel its ■ klebrigte 

 Feuchtigkeit . Neither has Petri seen my M. extensor as a separate muscle in .4canthias (see his fig. 5, j5, and the descrip- 

 tion p. 302); but it is also to be acknowledged that in this species it is ver\- closely connected with the M. dilatator, especially 

 proximally. 



2) Throudhjemske Selskabs Skrifter II, 1763, p. 319. 



3) Danmarks Fiske vol. Ill, 1S52— 53, p. go8. 



4) Muller & Henle, System. Beschr. der Plagiostomen, 1S41, p. 86, say: < Kein Dorn an den maunlichen .\nhangeu>; 

 founded, I suppose, on young specimens, in which only tlie soft dermal flap is seen. 



,sj Hist. nat. des Poissons, vol. I, 1865, the atlas, pi. IV, fig. 13. 



