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



The ventral terminal piece (fig. i 7>', fig. 6, 7) is considerably larger; the surface towards the 

 appendix-slit is deeply hollow like a trotigh, the external, ventral, surface is rounded, and has laterally 

 a winglike, sharp process; it is also completely calcified, and a great part of the surface is irregularly 

 furrowed and rugged. The one anterior edge of the trough articulates with the ventral marginal 

 cartilage, b\- the inner, ventral, edge it is connected with the style. 



Between this piece and the overlapping plate of the ventral marginal cartilage is seen a 

 third terminal piece (fig. i, T'j), the thorn or spine (fig. 8, 9). It is, like the other pieces, quite 

 hard, and the proximal end is somewhat head-shaped with a smooth surface, almost like an articular 

 surface; else it is for a great part ver)- irregularly rugged and furrowed, but the outermost point is 

 glossy and smooth, dentine-like; the whole thorn is longitudinally somewhat twisted. 



Besides these fully developed terminal pieces indications of two more are to be seen, viz. a 

 thin, narrow lamella, only calcified in spots, joins the lateral edge of Td^ and supports the edge 

 of the dorsal lip of the appendix-slit; anteriorly it reaches somewhat beyond Td\ this indicated piece 

 is here designated as Td^ (comp. pi. V, fig. 61, 62); the second piece is a very firm and strong fibrous 

 tissue, joined to the anterior dorsal edge of the piece Tr', and without distinct borders merging into 

 the aponeurotic covering, connecting the thorn, the piece Tv ^ and the overlapping plate of the mar- 

 ginal cartilage, and serving for insertion of part of the muscles (see pi. V, fig. 61, 62, Tv^); in this 

 latter piece a calcification has commenced, indicating perhaps, that it might become a separate termi- 

 nal piece, which I shall designate as Tt', (comp. other Plagiostomes for inst. Spiiiax). As these two 

 last mentioned pieces are, as it were, still developing, I suppose, that even the most developed of the 

 appendices in hand cannot, in a stricter sense, be said to be full grown }-et; but as the piece TV2. also 

 in some other Sharks (f. inst. Acanthias) is found only indicated and uncalcified, even in quite deve- 

 loped appendices, my supposition is not quite reliable. 



The whole of this terminal skeleton, composed of the terminal pieces and the end-style of 

 the stem, is movable to a certain degree; as to further details on this point the reader is referred 

 to p. 14. 



By examining the appendix-skeleton in the earliest stages of development we find that 

 originally it is composed of only one single piece, being that, which above is termed the appendix- 

 stem. This (in the specimen from Iceland, 2™ '^o"^ long, and in the specimen from the Zoological 

 Museum, 9 ft. long) is still quite soft, shorter than the basale, anteriorly rounded, posteriorly lance- 

 olate, the edges of the lancet being placed almost dorsally and ventrally, and ends as a thin style 

 (see fig. 2 in the text p. 19); thus mainly rendering the form of the chief piece minus the marginal 

 cartilages. Of these latter as well as of the terminal pieces no trace is found. In somewhat more 

 advanced stages, where the appendix-stem is as long as, or a little longer than the basale, the three 

 terminal pieces and especially the thorn are very well to be distinguished, while the marginal cartilages 

 still are absent, or, at all events, in the fibrous tissues, occupying their place, no calcification or distinct 

 bordering of such cartilages is to be found (not eyen of the overlapping plate). In still a little 

 more advanced stages also the marginal cartilages are found in the same shape and with the 

 same bordering as in the most developed, but the boundary lines between them and the stem are 

 much more distinctly marked; they are calcified, but are still soft enough to permit of easy cutting; 



