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



long, triangular, plate-shaped prolongation, Rd, fig. 45, running into the terminal part, and .supporting 

 the above-mentioned dermal fold. 



The number of terminal pieces is five, and to these is to be counted a «covering piece > be- 

 longing to the aponeurosis of the Jl/iisc. dilatator. This covering piece ') (fig. 48) is chiefly situated 

 on the dorsal side, has a fairly triangular contour, flatly rounded, with part of the medial edge bent 

 in such a manner that it catches round the medial edge of the end-style (fig. 46, d). This piece quite 

 evidently belongs to the same kind of structures as those, described as 'covering pieces in the be- 

 fore mentioned forms [R/uiia , Miiste/us ajitarcticns^ Torpedo., Xarc///r, Trygoii)^ only the development 

 having here taken place in the dorsal side of the aponeurosis; and .so I here (and in other Raja- 

 species) mark it with a d. 



With the distal end of the dorsal marginal cartilage is only connected one piece, proximally 

 also touching the style; I regard it to be corresponding to the Td of the other Plagiostomes, as it is 

 situated in the same manner as that in the dorsal lip of the appendix-slit, and shows the same relations 

 to the marginal cartilage and the stem; it is rather thick, somewhat bent in a crescent-shaped manner 

 with the concavity towards the stem; distally it is firmly connected with the style of the stem by 

 means of an uncalcified (or slightly calcified) cartilaginous prolongation -^j. With the hinder half of 

 the lateral edge of this piece Td is connected a long, narrow piece, attached by a band to the terminal 

 end of the style; it is situated in the edge of the dorsal lip, and I think it to be corresponding to 

 the piece, which in several other Plagiostomes I have called Td^. With the ventral marginal carti- 

 lage are terminally and laterally connected two pieces of a peculiar shape. Only the medial one of 

 these is also connected with the style of the stem, passing closely along it until the above mentioned 

 calcified bulb .r; this piece then must be corresponding to Tv\ it is rather thin, rounded on the outer 

 side, and prolonged to a slender, bent, obliquely-posteriorly and laterally directed part, ending in a 

 hook (it is this hook, which is seen covered by a loose, mucous membrane in the fig. 24 of the text 

 at Tv). The other piece consists of a crescent-shaped, large part, the concave side of which is for a 

 long way connected with the terminal and lateral edge of the ventral marginal cartilage; most ante- 

 riorly the long horn of the crescent reaches into the appendix-slit; behind and laterally the piece is 

 prolonged to a long, rather slender process, tapering to a somewhat bent, flat part with a slightly 

 notched end (it is this process, which is seen covered by loose, soft membrane in the fig. 24 of the 

 text at Tvi). I take this piece to be homologous with the fully developed piece Tv^. in Spinax (in 

 Acanthias and Soiiiiiiosiis it is only indicated), and its situation seems to me to settle this homology 

 beyond doubt. Finally is found, belonging to the ventral structures, a very large piece, rather crescent- 

 shaped when viewed from the ventral side, which must be corresponding to the piece T^ (the «thorn» 

 or <spur.> in different Sharks); proximally it reaches far into the appendix-slit, is on its medial side 

 broad, flatly rounded, and sends forth laterally a high, sharply winglike ridge with undulating, finely 

 indented edge; somewhat above the middle it sends forth a tap-like process, ventrally overlapping 

 Tv^; distally it ends with a plate resembling the blade of an axe, and ventrally reaching over the 



■) It is mentioned by the way by Moreau I.e. p. 251 under Raja clavata by the name of < Cartilage inteme»; the 

 presence of Td2 is also noted here, but this piece gets no special name, as it is not found in A', clavala. 

 2) This connection-piece I take to be not independent. 



