ON THE APPENDICES GENITA] BS (CLASPERS) IN THE SELACHIANS. 



27 



2. Special Part. 



Selachoidei. 

 Spinacidce. 



Acanthias vulgaris Risso. 



(PI. I, fig. 10, 11.) 



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 may refer to 

 Petri 1 ) (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 gradually, 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 2 ) and Homesj. In a specimen of the length of 64 cm the 

 following measures were found: 



Length of the appendix (from the fore-edge of the cloaca) . . 6,5 cm 



part free of the fin 3) icm 



terminal part 2, 2Cm 



appendix-slit 4i 2Cm 



Breadth of the appendix ab. i cm 



The skeleton has not been cpiite correctly described by any of the earlier authors + ). 



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

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

 medially with b t ; 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 b l , 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 -\- b z , and proximally towards 

 its articulation with b 1 is found a ridge (at b 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 6 ), 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 



-I I.e. p. 300, pi. XVII. fig. 5, A. 

 '-\ 1. c. 178S, p. 9, pi. 2, fig. 1. 



3) 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 ami the appendages have been drawn in a position, which they scarcely naturally would 

 be able to have. 



4) Drawings are found not only in Bloch. Gegenbaur and Petri, but also in Molin: Sullo scheletro degli 

 Squali. pi. Ill, fig. 7; Memorie dell' 1st. Veneto, vol.8, 1859, but without any explanation or description in the text. 



= i Gegenbaur, fig. 16, b\ Petri, fig. 5 D, >■'. 



•' Gegenbaur, fig. 17, /; it has been quite overlooked by Bloch and Petri. 

 1 Men tinned neither by Gegenbaur nor Petri. The hindmost end of it is the Processus a am Schienbein» 

 0- c. fig. 31 of Bloch. Neither of these authors have seen independent marginal cartilages in Acanthias. 



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