8 ON THE APPENDICES GENITALES (CLASPERS) IN THE GREENLAND SHARK. 



in the middle, and here projects from the posterior edge a clumsily rounded process. The stem of 

 the ventral articulates by its principal piece, the basale, (pi. I, fig. i i?), with the lateral end of the 

 pelvis, as do also a pair of the foremost rays. The foremost ray {R) is ahvays short and 

 big, shaped like the blade of an axe, whose head articulates with the pelvis, the hindmost corner of 

 the blade with two small terminal joints; it bears the second ra}-, which is accordingh- out of connec- 

 tion as well with the stem as with the pelvis; sometimes it is proximally coalesced with 7i. The third 

 ray has pressed so far forward, that it articulates both with the stem and the pelvis. Most of the 

 other rays are more or less straight, cylindric, distally a little flattened (especially in the foremost 

 ones); the two (less frequently three) hindmost are always somewhat bent, so that the conve.xity turns 

 dorsally, owing to the fact, that the glandular bag from the dorsal side passes under them to the 

 ventral side of the fin. These two hindmost rays are often more or less imited, sometimes almost 

 quite coalesced. The foremost rays (more than half of them) have three joints, then follow some (3) 

 with two joints, and the last (3) are never jointed. The number of rays varies from 12 — 16'); com- 

 monly one fin of the same pair has a ray more than the other, and a rather considerable variation 

 is found in the more special relations of the rays, in their mutual coalescing ^j, their articulation, and 

 distal dichotomy; sometimes an extra ray is inserted, not reaching the stem; such extra rays have 

 not been counted in the numbers given, and they do not occiir symmetricalh" in both fins. Such 

 variations are also known in other Sharks 3) , and I shall not here enter into further details , as they 

 are of no importance for the examination in question. 



The stem consists of i) a large and big principal piece, Basale nictapterygii {B), to which 

 most of the rays are attached; its inner edge is almost straight, onh- slightly concave, the outer edge 

 is convex; 2) a short piece {62) directly continuing the foregoing; 3) generally is on the medial side 

 inserted, as it were intercalated, a little cuneiform piece (di). The piece ^2 bears the two hindermost 

 rays, so that the last but one is articulated at its proximal extremity, and here also touches the ba- 

 sale, the last at its distal extremity, where it has also a little articular surface with the proximal 

 end of the stem of the appendage. Finally is found 4) a rather considerable piece (/J) placed on the 

 dorsal side of the stem in such a way, that it is proximally connected with the latero-dorsal corner 

 of the basale by a little articular surface, and distall)' by a longer, obliquely placed articular surface 

 with the latero-dorsal edge of the anterior end of the appendi.x-stem (fig. 2 at :r). This piece /? is 

 rather thick, dorso-ventrally somewhat flattened, has a convex medial edge, and a straight lateral 

 edge; posteriorly it is somewhat more pointed than anteriorly; the foremost part of the convex edge 

 is connected with the dorsal side of the piece 62 ', it has no articulation at all with any of the rays ■>). 

 Between the lateral corner of ^2, /?, and the appendixstem 5) a little piece 6-^ is sometimes intercalated. 



Then follows 6) the appendixskel eton. Its chief piece (tab. I, fig. i 1^, fig. 2, 3) evi- 

 dently belongs to the stem, and is placed in immediate continuation of the foregoing pieces, with 



') In two females I have found the number respectively 15—17 and 16 — 17 on the two sides. 



2) In one specimen separate, independent pieces of cartilage have been developed; they are placed across, and near 

 the outer end of the rays they connect two and two of these. 



3) Conip. Gegenbaur: Ueber das Skelet der Gliedniaassen der Wirbelthiere ini Allgemeinen uud der Hinter<;lied- 

 maassen der Selachier insbesondere. Jen. Zeitschr. 5 Bd., 1870, p. 435 seq. 



4) By the choice of the letter-marks I have intended to ])oint out, that all these parts belong to the stem-skeleton. 



