ON THE APPENDICES GENITALES (CIvASPERS) IN THE SELACHIANS. 27 



2. Special Part. 



Seldchoidei. 



Spinaciihp. 

 Acanthias vulgaris Risso. 



(PI. I, fig. 10, II.) 



The common picked Dog-fish has been so often examined that I think a more particular de- 

 scription of the external features of the copulatory appendages to be superfluous; I ma)' refer to 

 Petri') (with regard to whose description, however, I must remark that the investment with dermal 

 teeth at the places of transition to naked parts does not cease gradualh', but is quite sharply bounded; 

 the dorsal side is wholly naked, as is also on the ventral side the hindmost point of the terminal part), 

 as also to the earlier description by Bloch-) and HomeJ). In a specimen of the length of 64'^'" the 

 following measures were found: 



Length of the appendix (from the fore-edge of the cloaca) . . 6,5<^'" 



— - - part free of the fin 3,1'' 



— - - terminal part 2,2'= 



— - - appendix-slit 4,^"™ 



Breadth of the appendix ab. 1'='" 



The skeleton has not been quite correctly described by any of the earlier authors 4 j. 



Between the basale and the appendix is found only one short joint (/^,), and besides the dorsal 

 piece /?5); this latter articulates anteriorly with the basale, posteriorly with the appendix-stem d, and 

 medialh- with (5,; its lateral edge is convex, projecting somehwat in the shape of a roof over the two 

 hindmost rays; these rays are borne by the piece /', , and are often coalesced; they are stronger and 

 longer than the last ray but two, which latter comes from the basale. 



The stem of the chief piece of the appendix has a length like B -\- 6„ and proximally towards 

 its articulation with /^, is found a ridge (at d in fig. 10) projecting in a somewhat keel-like manner; 

 in the hindmost half it has laterally a little trough-like hollow. The soft end-style is short*^), flatly 

 rounded, and reaches not nearly to the end of the terminal part. The dorsal marginal cartilage?) 

 (Rd) can forward be indistinctly traced as a rounded ridge to about the letter x in fig. 11 (it is more 



rem 



octn 



■) 1. c. p. 300, pi. XVII, fig. 5, ^. 



-) 1. c. 1788, p. 9, pi. 2, fig. I. 



.>) On the Mode of breeding of the Ovoviviparous Shark etc. Phil. Trans. 1810, Pt. II, p. 205, pi. IX and X; in the 

 lastmentioned place the ventrals and the appendages have been drawn in a position, which they scarcely natnrally would 

 be able to have. 



41 Drawings are found not only in Bloch, Gegenbaur and Petri, but also in Jlolin: Sullo scheletro degli 

 Squali, pi. Ill, fig. 7; Memorie dell' 1st. Veneto, vol. S, 1859, but without any explanation or description in the text. 



5) Gegenbaur, fig. 16, i; Petri, fig. 5 Z), r'. 



6) Gegenbaur, fig. 17, t\ it has been quite overlooked by Bloch and Petri. 



7) Mentioned neither bv Gegenbaur nor Petri. The hindmost end of it is the Processus a t.ani Schienbein > 

 (I.e. fig. 31 of Bloch. Neither of these authors have seen independent marginal cartilages in Acanlliias. 



4* 



