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30 



longer ray at the lower edge, in addition to the 10 rays developed. All the rays 

 are unbranched, but linely threaded at the ends (the same applies to the rays of 

 the ventrals and the other fins). The uppermost rays are the longest and strongest 

 in all the species; the breadth of the rays decreases evenly towards the lower 

 margin; the lowermost ray and the uppermost 2-4 are quite unarliculated, the 

 remainder distinctly articulated though in extremely varying degree. 



The pelvic bones (fig. 20) can be seen in all the species through the sharp 

 ventral margin, always in the 8th ventral plate. On the lower edge of the latter 

 there is an incision into which is fitted the lower margin of the pelvic bone, and 

 the ventral fins are attached here; if this plate is fused below with an unpaired 

 element, the latter can therefore not extend any further back than to the ventral 

 fins. The pelvic bone can be followed from this place, directed obliquely forward, 

 as a quite thin, apparently rod-shaped process up through the transparent ventral 

 margin and can further be traced more or less distinctly higher uj), crossing the 

 rachis of the 8th plate; its upper end is not as a rule seen through the skin, as 

 it is hidden in the muscular mass. In A. strigala it seems to be placed in a some- 

 what more vertical position than in the other two species and may lie almost 

 parallel to the above-mentioned rachis. 



Closer examination shows that each half of the pelvics greatly 

 resembles a fin-ray; it is a quite thin and narrow bone, broader at 

 the base and here with a cartilaginous lower edge, to which the ven- 

 tral fin-rays are attached; the cartilage continues from here as a thin 

 axis through the whole bone, the upper end of which again is carti- 

 laginous. The portion of the bone which surrounds the cartilaginous 

 axis is somewhat thicker and thus more prominent than the remaining, 

 thinner surface; it separates — like the muscular ridge on an inter- 

 spinous bone — the anterior and posterior muscles (or muscular ten- 

 dons) for the rays of the ventral fhis. In A. strigata (and probably 

 also piincliilata) the whole pelvic bone is somewhat broader than in 

 scutata, where it is extremely narrow. Long muscular tendons lie, as 

 above menlioned, along the anterior and posterior lateral surface, 

 separated by the faint axial thickening, and also on the inner side of 

 the half facing forward — thus between the two halves of the pelvics 

 (corresponding to the ventral musculature on the pelvics of a typical fish). The 

 muscular fibres which move the rays of the ventral fins by means of these tendons 

 form a muscular mass, which as mentioned above hides the upper ends of the 

 pelvic bones, and the main portion at any rale takes its origin from the inner 

 wall of the abdomen. This pelvic region thus seems quite diOerenl from that of 

 all other bony fishes in regard to position, form and arrangement of the muscles. 

 The position and something of the form will however be found again in Cenlriscus. 

 The large amount of compression suffered by the abdomen in Amphisile has ob- 

 viously infiuenced the form and position of the pelvic region and thus made it 



Amphisile stri- 

 gala. Left pu- 

 bic bone, seen 

 from outside. 



