39 305 



representing two fused hypurals and the urostyle, and embraced by 7 fin-rays; the 

 latter are all really ventral to the end of the chorda. The dorsal iiiterspinous bones 

 are relatively longer, the spinous processes lower than in Siphonostoma ; they pos- 

 sess similar but more regular expansions (cfr. Pi. IV, fig. 12). Anal fin and anal inter- 

 neurals are wanting. 



Nerophis ophidian has similar vertebrae to the preceding species; only the 

 last caudal vertebra is without any plate, the caudal fin being absent. The 

 dorsal fin is for the greater part situated on the tail. A specimen (Ç) with 34 

 dorsal rays has its dorsal fin supported by 11 vertebrae, 3 abdominal and 8 caudal; 

 the grouping of the interneurals is the following: 



3, 3, 4 3, 3, 3, 2, 3, 3, 4, 3. 



The caudal vertebrae, except the last, are provided with haemal arches; the 

 last vertebra is rudimentary, without any processes save an indication of transverse 

 processes. The number of caudal vertebrae in this specimen is 74! 



In Hippocampus the vertebrae are shorter and stouter than in the preceding, 

 elongated genera, but the general shape is the same. Also here the 3 anterior are 

 immovable and first and second firmly joined to the clavicle. In the two species 

 examined (//. brevirostris and longirostris) there are 11 abdominal vertebrae; the dor- 

 sal inlerspinous bones are connected with the two foremost caudal vertebrae (H. brevi- 

 rostris, PI. IV, fig. 2) or besides with the last abdominal [longirostris). The first caudal 

 vertebra has a hæmal arch but open below, sometimes joined to the next, which 

 also may be open below. The hæmal arches of the two anterior caudal vertebrae 

 are directly in connection with the inlerspinous bones for the anal fin (PI. IV, 

 fig. 2). The secondary transverse process is very long, only separated by a narrow 

 slit from the primary one on the vertebrae supporting the dorsal fin. The hæmal 

 arches are considerably stouter than in the elongated genera, and, as the vertebræ 

 are shorter, the protection of the large subcaudal blood-vessels is much the same 

 as in other fishes. The spinous processes are somewhat more strongly marked than 

 in the other genera. The last vertebra rudimentary. 



In H. brevirostris (c?) the number of vertebræ is found to be: 37 = 11 + 26. 



The 15 (//. brevirostris) or 16 (H. longirostris) dorsal inlerspinous bones are 

 bisegmented; the distal segment is a small cartilage; the proximal segment longer 

 than in the preceding genera; the lateral expansions for connection with the 3 upper 

 lateral plates of the armour are directed obliquely downwards. The row of inter- 

 neurals is rather densely crowded, but two fanshaped groups may easily be distin- 

 guished, one for each supporting vertebra (8 and 7 members). In each group the 

 lateral expansions are directed towards the middle, pointing backwards on the ant- 

 erior members and forwards on the posterior. 



The anal fin in H. brevirostris has 3 bisegmented inlerspinous bones (not fused 

 together); the terminal segment is a small cartilage, the proximal is long, reaching 



