36 



ON THE APPENDICES GENITALES (CLASPERS) IN THE SELACHIANS. 



M. compressor. The bag-formed part of this muscle is rather long, and reaches considerably 

 forward of the pelvis. On the contrary, the part forming the -outer lip-muscle > is rather small 

 (smaller than in my figures); as usual it originates from the stem-skeleton (0) and from the hindmost 

 raws, and is inserted on the proximal edge of the ventral marginal cartilage; it will here scarcely be 

 able directly to contract the dilated terminal part 1 )- 



o 



*— 



f- 



Pristiurus melanostomus (Bonap.). 



(PI. II, fig. 20, 21.) 



The ventrals of the male of this species are also dorsally coalesced in a similar manner as in 

 the preceding two Scylliidse 2 ), but to a still less extent than in Sc. stellar r, and a deep curve separates 



the coalesced part into two fin-laps. The appendices reach far behind the fin- 

 membrane 3), in a specimen of the length of 7S cm to 23 mm behind the point 

 of the fin-membrane; the whole length, from the hindmost edge of the 

 cloaca, is 50 mm ; the part quite free of the fin is 35 ,nm long; the largest 

 breadth of the organ is about 7 min ; the terminal part has a length of about 

 25""". The ventral side is covered with dermal teeth, except the hindmost, 

 soft, as it were, convoluted part (abt. q mm long), on which still scattered 

 groups of teeth may be seen; the dorsal side is naked, as are also the 

 adjoining parts of the medial side, where they are covered by the fin- 

 membrane; on the free edge of the lip / a few scattered rows of dermal 

 teeth are seen. The dermal teeth are generally very fine; as in the fore- 

 going species their points are on the terminal part turned towards the 

 base of the appendix. The dentition on the coalesced fin-parts is as in 

 Sc. stellare. 



The peculiar appearance of the appendix will be seen with sufficient 

 distinctness from fig. 9. The furrow anteriorly is opened by a large, easily- 

 distended slit of a length of 8 — io mm ; behind this slit it is closed for an 

 equal length, and again open in the terminal part. In spite of the great 

 dissimilarity in general when compared with the appendix of the preceding 

 Scylliidse, a closer examination will show a rather considerable similarity with 

 these, especially with Sc. stellare: corresponding to the peculiar process /of the Scyllia is found a thin, 

 soft dermal process, which may be folded towards the furrow (as in fig. 9), or spread in a wing-like 



This part of the M. compressor has been quite overlooked by Petri, who has seen and drawn the other muscles, 

 and given them the following names (see I.e. pi. XVII, fig. 7, A and B|: 



The muscle here marked A (the chief portion of the .1/ adductor] = fl.nt.p. i.e. flexor tnajor pinna. 



— - — cii = fl.fi. t. i.e. flexor pierygopodii biceps. 



— - — a 2 = Jl.p.ex. i. e. flexor pterygopodii exterior. 

 The M. extensor here marked E — fl.fi. /. i. e. flexor pterygopodii interior. 



What Petri calls flexion must, I think, rather be regarded as an adduction connected with an extension of the appendix. 



i T1k- expression used by Lilljeborg I.e. p. 66o their inner edges are not coalesced is accordingly not quite 

 correct. The appendices are shortly described at p. 662. 



1 Comp. f.unnerus: <'m Haae-Gselen, pi. I, f. (Trondhjemske Selsk. Skr., II. 1 



Fig. 9. 



Pristiurns melanostomus. 



The right appendage seen 

 from the dorsal side; about 

 the natural size. The fin- 

 membrane is cut through, 

 and thrown back. the 

 larger basal opening of the 

 appendix-slit; between the 

 asterisks it is closed by 

 coalescing. The other signs 

 as in fig. 8. 



