_, ON THE APPENDICES GENITAEES (CLASPERS) IN THE SELACHIANS. 



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regard to a comparison with those mentioned in the Plagiostomes as belonging to the appendix; as 

 to the other mnseles I may refer to the thorough description by v. Davidoff (I.e. p. 473 seq.). 



Between the two halves of the pelvis a broad band (fig. 69— 71, s) is stretched, which, as it 

 were, supplements the hinder surface of the pelvis; anteriorly this band is attached along the whole 

 concave posterior edge of the pelvic arch, and laterally it reaches almost to the articulation between 

 the pelvis and the basale; in the median line it is somewhat thickened as a firmer tendinous stripe. 

 From the whole ventral surface of this band as well as from the ventral surface of the pelvis arises 

 the ventral layer 1 ) of the group of muscles representing the M. adductor (et depressor) pinntv in the 

 Plagiostomes; in the middle line a stripe broadening somewhat backward, is left uncovered (see fig. 70). 

 This muscular layer is composed of bundles that are distinctly seen distally. Of the medial and hind- 

 most fibres of this layer only the deepest-lying are attached to the ventral side of the basale, to the 

 thickened medial edge of this piece, from which edge the ventral ray-muscles (Ra, fig. 70) arise; other- 

 wise the greater portion of the medial fibres of this muscular layer is attached to these ray-muscles 

 until a line of insertion , distinctly seen in fig. 70. The foremost and lateral parts of this muscular 

 layer pass, without any bordering -- neither in the depth — , into the ventral ray-muscles, as is also 

 the case in the Plagiostomes 2 ). The other muscular mass 3) which together with the foregoing one 

 forms the M. adductor in the Plagiostomes (fig. 69, 71, A), arises from the dorsal side of the above 

 mentioned tendinous band, as well as from part of the dorsal surface of the pelvis (viz. until the 

 slight crest that separates it from the muscle m of the pelvic appendage); this layer is thicker than 

 the ventral one , and attaches to the thickened medial edge of the basale and to the piece b t , espe- 

 cially with a powerful portion of fibres to the large process x of this latter piece; 011 the ventral 

 side it reaches to the muscle D, which corresponds to the M. dilatator, and will be more particularlv 

 mentioned hereafter. A special ]\F. extensor has not been separated. 



A far as I am able to see, only two+) muscles are found 011 the appendix-shaft, one corre- 

 sponding to the M. dilatator (D) in the Plagiostomes, the other to the muscular investment of the 

 glandular bag (inclusive of the 1 outer lip-muscle ), M. compressor sacci (S). 



The J/, dilatator arises anteriorly with its ventral portion from the hinder end of the basale, 

 but with its other parts only from the piece b l , at some distance from the articulation between this 

 piece and the basale. Almost all the fibres run straight from before backward; only on the ventral 

 side some of them bend laterally; they are attached on b close to the base of the lateral and medial 

 branches of the terminal part, and a few fibres go to the skin covering the skeleton; on the 



'I Oberflachliche ventrale Schicht, ssv, fig. 16, 17, pi. XXIX, v. Davidoff. 



-\ I find upon the whole that the difference as to the arrangement of the ventral part of the M. adductor in Chi- 

 mara and in the Plagiostomes is only in degree; in many of these latter (Scy/lium, Pris/lurus, the Rays), the superficial part 

 of the ventral layer of the M. adductor stretches quite over the ventral side of the basale and more or less out on the ray- 

 muscles, v. Davidoff describes this .ventral muscular laver in Cliiiuara as stretching considerably farther laterally on the 

 fin than is really the case; and his words (1. c. p, 474): Zum Basale hat er gar keine Beziehung etc., are not correct. 



si The apelvico-basale Fasern of v. Davidoff, fig. 15. 17, Pb\ they do not, however, as he thinks, arise exclusively 

 from tin- pelvis. 



M v. Davidoff, I.e. p. 4S0, counts three, which he moreover calls vollkommen gesondert , viz. a ■Flexor , an Ad- 

 ductor , and an Abductor ; in three specimens of Chimcera that I have examined, I have not been able to find a real se- 

 paration between the two first-named; but even if such a separation might appear, it will be of only slight importance with 

 regard to a comparison with the Plagiostomes (as surely also with regard to its functions); at all events, « Flexor + Adductor* 

 v. D. is = M. dilatator; the AMuctor of v. Davidoff is the muscle of the glandular bag. 



