. British and Irish Salmonidæ. Salmonidae. FRESH-WATER TROUT—JAWS AND FINS OF. 187 salmon (p. 57 a?i^e),tliis ^rowtli, consisting of iibrous connective tissue, increases at the brccdinfT period, and in seven-year-old lisli at Ilowietoun it is in advunco of the upper jaw when the nioutli is closed, ofleu formlnf,' a sore surface in front of the preinaxillaries. In measuring tlic proportions of the parts ol the head of several specimens I found that whereas the lower jaw was as long or very nearly as long as seen in old lish, the distance from the nostrils to the end of the snout only equalled
. British and Irish Salmonidæ. Salmonidae. FRESH-WATER TROUT—JAWS AND FINS OF. 187 salmon (p. 57 a?i^e),tliis ^rowtli, consisting of iibrous connective tissue, increases at the brccdinfT period, and in seven-year-old lisli at Ilowietoun it is in advunco of the upper jaw when the nioutli is closed, ofleu formlnf,' a sore surface in front of the preinaxillaries. In measuring tlic proportions of the parts ol the head of several specimens I found that whereas the lower jaw was as long or very nearly as long as seen in old lish, the distance from the nostrils to the end of the snout only equalled 1-^- diameters of the eye, whereas in old salmon it eciuals 2 diameters of the orbit. At Howictoun my observations had to stop at this point as fish over this ago are not kept, but it was clear that should the upper jaw extend in the same proportionate length as in the salmon, the knob would be inside, not outside the mouth. In Atigust, 1883, I received from Mr. Arthur,* of Otago, an old male trout, S. fario, weighing 21 lb. and 32 in. in length, and this completed my series, the upper jaw had elongated as in the salmon and the hook was now inside the mouth. Whether this soft hook ever completely absorbs is questionable, but the older the fisli the larger the knob, and in very old specimens, due to an elongation of the bones of the snout and upper jaw, it is found inside the mouth ; here it may cause ulceration, impossibility of moving the preinaxillaries, and death from starva- tion. In the mandible at its anterior end the rami arc ossified together without any appearance of a suture. Abroad groove (0-3 of an inch) passes from above down the front of the symphysis and having a crest or ridge along each side, this ridge being elevated above the plane of the dentary bone. Also anteriorly the foremost portion of the lower jaw has both turned as well as grown upwards and the teeth from one ramus to the other forms an unbroken band. The hook or knob is attached to the whole ext
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectsalmoni, bookyear1887
