41 



307 



provided with a hooked spine, pointing backwards. Also here the nuchal tendons 

 appear to be fixed to the supraoccipital; the braincase is upon the whole similar 

 to that of Hippocampus, but the snout is long and slender, and more than half its 

 length is due to the niesethmoid. 



In Syngnatlms the branchial apparatus is like that of Siphonostoma, but 

 in the other genera it differs considerably. In Nerophis (œqiiorens and ophidion) the 

 hyoid has only three pieces, the upper hypohyal, which in Siphonostoma is very 

 small, being lost; there is only one branchiostegal, which bifurcates distally and is 

 fixed to the inner side of the epihyal. The glossohyal is short but with long 

 anterior cartilage, the urohyal long and stout. The gill-bearing part is still more 

 elongated (PI. VI, fig. 12); there are the same two basibranchials, but the first arch 

 is provided with a hypobranchial, while all the following are devoid of hypo- 

 branchials; every trace of epibranchials is wanting, and the pharyngobranchials 

 are reduced to one on each side, probably representing that of the second arch. * 

 The gill-rakers are similar to those in Siphonostoma. 



In Hippocampus (PI. VI, fig. 11) {brevirostris and longirostris) the glossohyal (gl) 

 is very short, the urohyal short and stout; the hyoid and the branchiostegals as 

 in Siphonostoma. Basibranchials are totally absent. The first gill-arch possesses a 

 hypobranchial and an epibranchial ; the hypobranchial is longer than the cerato- 

 branchial, and provided with flat lateral expansions; it is almost parallel to its 

 fellow from the opposite side, or only feebly converging in front. The second arch 

 is complete, having a pharyngobranchial, in the third only the hypobranchial is 

 wanting. Thus, except the first arch, the gill-arches agree with those of Siphono- 

 stoma. The gill-rakers are somewhat longer than in the latter, but their ossified 

 axis is confined to the basal part only. 



The following tabular view of the genera examined will show the main 

 features of the branchial apparatus: 



Siphonostoma and Sgngnathus. 



■ Sometimes it may on the one side be divided in the middle by an articulation (representing 2d 

 and 3d pharyngobranchial?); upon the whole it is often somewhat differently shaped on the two sides. 



I). K. 1). VidensU Selsk. Skr., 7. Rickke, nalurvidensk. og mathem. Afd. VIII. .■;. 40 



