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



distinct, when the piece is dried); posteriorly it is distinctly elevated as an edge of the appendix-slit. 

 The \-entral marginal cartilage (Rv) is shorter, resembles the corresponding one in the Greenland 

 Shark, and has, as in the latter, a plate-like part") folded to the dorsal side; on the concave inner 

 side it has furthermore a strong, elevated process; in the furrow between this process and the folded 

 part the proximal end of the thorn is placed. 



There are four terminal pieces. 



TV-) is narrow, with the foremost part of its medial edge closely connected with the end-style, 

 and behind this with the edge of the ventral piece Tv; distally it takes the form of a flattened, sharp- 

 edged hook; this hook-shaped part rises uncovered through the skin, is smooth, shining, and dentine- 

 like. Ti/ is with part of its lateral edge connected with a quite thin, plate-formed pieces), Td^, also 

 anteriorl}- connected with the marginal cartilage Rd; it is placed in the skin forming the dorsal lip 

 of the appendix-slit of the terminal part, and corresponds to the piece TV,, indicated in the Green- 

 land Shark. 



The ventral terminal piece, Ti'-*), is considerably broader and longer than the dorsal one, 

 rounded on the ventral (outer) surface, hollowed like a spoon towards the appendix-slit; except the 

 hindmost part it is firmlv calcified; the foremost part of the medial edge is connected with the eud- 

 stvle, and behind this with Td, the hook of the latter lying freely in the outermost spoon-like end of 

 the former piece; in the j^roximal end it has medially an articular process for articulation with the 

 above mentioned process of the concave side of the marginal cartilage R71, and its lateral edge is 

 firmly connected with a strong, thin membrane (fig. 11, TV'j), serving in the foremost part for attaching 

 the outer lip-muscle of the glandular bag; this membrane then corresponds to the similar, but thicker 

 one in the Greenland Shark, and to the piece Tt'^ in Spiiiax. 



The fourth terminal piece, 7",, is the one called the ...spur^^?) by the different authors; with the 

 proximal, somewhat head-shaped end it is attached inside of the folded plate of the marginal cartilage 

 Rv to the above mentioned process, and to the proximal and lateral end of the piece Tv\ it is formed 

 as a triangular thorn or spine, longitudinally somewhat twisted, with two concave surfaces; it is firm, 

 shining, dentine-like, and the greater part of it is uncovered b}- the skin. It can be moved quite in 

 the same manner as the corresponding spine in the Greenland Shark. 



The muscular s y s t e m . The M. adductor shows the general typical relations. The M. extensor 

 reminds very much of the same one in the Greenland Shark; as in the latter it has here its origin 

 on the medial side of the basale and ^„ stretches over the tknee of the appendix-stem as a thin, 

 flat covering over the AI. dilatator^ and inserts itself along the boundar)' line of the dorsal marginal 

 cartilage. 



The M. dilatator originates proximally with a dorsal portion at the same place as the AI. extensor 

 and quite covered b}- it, that is to say some way up on the basale; on the ventral side its proxi- 



■) Block, Processus d\ Gegenbaur, fig. 15, 16, a; Petri, fig. 5, /?, E, pr\ regarded bj- all onh- as a process ou 

 the chief piece. 



2) Bloch, der Hakeii, fig. 2, e, fig.6; Gegenbaur fig. ]6, 17, o; Petri, fig. 5, /ik. 



3) Petri, fig. 5, la; it is neither mentioned nor drawn b}^ Bloch or Gegenbaur. 



4) Bloch: der breite Knochen, fig. 2, d, fig. 5; Gegenbaur, fig. 15 — 17, c\ Petri, fig. 5, />'" , he interpreting it as 

 the terminal joint of the stem. 



5) Bloch, der Sporn, fig. z, c, fi.g. 4; Gegenbaur, fig. 15, 16, a' \ Petri, fi.g. 5, s/> and ca. 



