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



mal origin accordingly is much more backward, at the distal end of the M. adductor; it is inserted as 

 usual, its aponeurosis being especially 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 M. compressor wrapping the bag, is much distended, and consequently 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 very 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 bodv, 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 Tz>, and consequently it acts antagonistically 

 against the M. dilatator, and at the same time lays the spur 7\ ' 1. 



Spinax niger Bonap. 

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



The very peculiar-looking appendages in this common Shark have singularly enough been 

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

 at all. Gunnerus 2 ), in his description of the «Sort-Haa», says: -they (i.e. the two Membra genitalia) 

 were supplied with some sharp bony spines, such as 1 have seen on the Membra of several Rays, 

 when the ends have been turned inside out. KroyerS) says: «At the end of the copulatory 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 they are hidden between a pair of small cartilaginous 

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

 correct description I have 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 by Kroyer appears in this figure as a thorn, although it is 



■l Petri (I.e.) designates this part of 1113- M. compressor as M. levator (fig- 5. ml), 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, however, is easily pointed out. Contrary to Petri, Bloeh upon the whole has a correct understanding 

 of the mobilitv of the spur, speaking (1. c. p. 131 of eiuen sehr sonderbaren Mechanismus. Davon mir wenigstens in der 

 Anatomie kein ahnlicher bekandt ist . Bloch has a chiefly correct description of the muscular system; 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 my M. adductor, the third M. dilatator + my M. 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 1 2 1 muscles expel its klebrigte 

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

 tion p. 3021; but it is also to be acknowledged that in this species it is very closely connected with the M. dilatator, especially 

 proximallv. 



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



3) Danmarks Fiske vol.111, 1S52 — 53, p. 908. 



■ 1 Miiller & Henle, System. Beschr. der Plagiostomeu, 1S41, p. S6, say: <Kein Dorn an den mannlichen Anhangen ; 

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

 5) Hist. nat. des Poissons, vol. I, 1S65, the atlas, pi. IV, fig. 13. 



