4 DUBLIN NATimAL HISTORY SOCIETY , 



DoMiNioK J. CoBEioAN, M. D., read the following : — 



ON SOME STRUCTTJEAL PECXrLIARITIES Of THE MOtTTH IN THE PIPE-FISHES 

 (SYNGNATHID^). 



( Vide Woodcut, post.) 



The spcciinen of the Syngnathus before us is dried so aa to preserve 

 and show a very beautiful apparatus which exists under the lower jaw, 

 and which I have not seen exhibited in any of the museum specimens 

 that have come under my observation, nor have I seen it described. 

 The apparatus to which I allude is, what may be called, a " Derrick 

 mechanism" for enlarging the opening of the mouth, and widening the 

 throat in the act of swallowing. 



As the Syngnathus is generally drawn orpreserved in museums (fig. 1 ), 

 the under line of the jaw is nearly horizontal, the under line of the profile 

 deviating little from the horizontal, and showing no projection ; and, 

 looked at in a vivarium, the aspect of the fish is the same, and the only 

 motion usually perceptible about the jaw is that of the singular-looking 

 fleshy. Up-like lower jaw, which projects upwards from the extremity, 

 with its valve-like action, opening slightly to admit water for respiration, 

 and then closing, to aid the action of the tubular jaw in driving the 

 water backwards through the gills ; but this limited motion would not 

 suffice for taking in food, and hence, when the Syngnathus is about to 

 swallow, the action of the mechanism I shall now describe is brought 

 into play. If the dried specimen be viewed laterally, a process {h, figs. 2 

 & 3), (glossohyal bone), about a quarter of an inch long, is seen projecting 

 downwards at right angles to the jaw. If, instead of the lateral view 

 this process be looked at in front, it is seen to consist of two limbs, or 

 processes, like those of a derrick — one springing from the lower jaw on 

 each side, and uniting at an angle in tbe centre {b, fig. 2). From this 

 point of junction, which appears to be ligamentary, an elastic tissue (a) 

 extends along the mesial line between the two sides of the lower jaw 

 to the valve-like lip, while behind a muscular tissue (c), stretches back- 

 wards from the point between the operculum to (/) what I believe is the 

 OS hyoides (h). When the animal is alive, the action of this mechanism is 

 very beautiful. In the mere process of breathing this apparatus does 

 not come into view at all. It lies quite hidden within the triangular 

 space within the lower jaw, and fits it, and fills the space so accurately 

 that it is very difficult to detect it; and even in the dead specimen the 

 action of this elastic tissue keeps it so accurately fitted in its berth, that 

 it may escape a very close examination. To return, however, to the 

 living animal. , 



"When the Syngnathus is about to swaUow, it draws out by mus- 

 cular action the point of this derrick, as we may call it, from its 

 receptacle. In so doing, the point of it draws with it the ligamentaiy 

 tissue extending to the lower lip until the point is drawn down, so as to be 

 at right angles with the jaw ; the lower lip is necessarily di'awn down- 

 wards and backwards, so as to widen the orifice of the mouth, and the 

 fish, with the process projecting downwards, is then such as is scon in 



