29 295 



neural arch only in front adapted for suturai connection with the preceding vertebra ; 

 the connection with the following being the same as that between the remaining 

 abdominal vertebrae. These are in the main of one type, except the hindmost. 

 They are long and slender, witli long, flat and narrow, generally pointed trans- 

 verse processes; the base of this process broadens gradually along the anterior half 

 of the vertebra, more and more as we pass backwards, on the hindmost vertebrae 

 almost reaching the front margin. 



The spinous process is a low thin crest, in the middle over the level of the 

 transverse process rising a little to form a vertical point. Articular processes are 

 wanting, at most indicated as feeble undulations on the margins of the neural 

 arches. 



The hindmost abdominal vertebra (the 19th, PI. IV, fig. 6, 7) supports the front 

 part of the dorsal fin, but in different individuals a greater or lesser part; in struc- 

 tuie, therefore, it corresponds to the 8 following caudal vertebrae, supporting the 

 remaining greater part of the dorsal fin, but with the exception that it has no 

 inferior arch. The triangular transverse process reaches basally along the whole 

 anterior half of the vertebra, and backwards it extends along the lower margin of 

 the corpus in the shape of a wing, rounded in outline (v). The spinous process 

 as in the preceding vertebrae forms a thin longitudinal crest, but the upper margin 

 of the latter carries some deep and narrow incisions (in the case figured two), 

 strengthened along their margins with thickened ribs. Into each incision fits an 

 interspinous bone. In some cases only the foremost interspinous bone is fastened 

 to the posterior margin of the spinous process and for the rest to the following, 

 the first caudal. The 8 (or 9) anterior caudals (PI. IV, fig. 8, 9) show the same 

 type as the last abdominal; only they are shorter, and the anterior extension of 

 the transverse process is on the same level as the posterior wing; besides they 

 possess inferior arches. The latter originates from the underside of the transverse 

 process proper (fig. 9), near its hind margin; on the first caudal vertebra the distal 

 ends of the arch may be separate and in position oblique towards the tail, while 

 all the following form a short, vertical, inferior spine. Very often the first caudal 

 vertebra has no inferior arch or only an indication of its basal part. The upper 

 spinous processes each support 4 or 3 interspinous bones, the 8th, and sometimes 

 also the second, 5. On the 8th caudal the posterior transverse wing is narrow and 

 on the following it is wanting; evidently this structure is developed together with 

 the muscles for the dorsal fin. As is well known the principal motor apparatus 

 in the Syngnathids is the dorsal fin; to produce the powerful undulations of the 

 latter the muscles to the fin rays are greatly developed, forming a voluminous 

 layer inside the body muscles, separated from the latter by a pigmented membrane 

 of connective tissue; the fin-muscles belonging to the outer part of this layer are 

 basally attached to the transverse processes and their wing-like expansions. The 

 remaining caudal vertebrae behind the dorsal fin are of one type, long and slender, 

 with low dorsal crest, in the middle provided with a small vertical spine; the trans- 



