304 38 



immovably joined to the lateral and inferior lateral plate, those of the outer face 

 to the dermal part of the clavicle and to the "cover-plate". In this way the 

 structural arrangement before-mentioned is brought about; the whole part, on 

 which the pectoral rays play, is solidly fastened between the lips of the slit in 

 the armature. Through the narrow apertures left between the component skeletal 

 parts the tendons pass from the pectoral muscles to the base of the fin-rays, thus 

 arranged between and conducted by a system of "coulisses". In this way the whole 

 scapular system is strengthened by the dermal armature, and the extremely thin 

 and fragile, mostly cartilaginous, apparatus is rendered capable of forming the base 

 for such powerful muscles as are really found here. 



The peculiar structure of the pterygials and the mechanical part it plays, 

 has hitherto escaped attention; only Parker has observed the bony processes, 

 which he compares with stag's-horns without understanding their functions. 



The cleft base of the fin-rays embraces a small nodule of cartilage, which 

 forms the joint with the cartilaginous mass resulting from the fusion of the distal 

 ends of all the pterygials. 



The (14) pectoral rays are as usual composed of two lateral halves, but un- 

 jointed and unbranched. 



Osteology of other members of the Syngnathidæ. 



In the other Syngnathids which I have examined the main features of the 

 vertebral column are the same as in Siphonostoma typhle: i. a. the vertebrae sup- 

 porting the dorsal fin are always provided with a secondary transverse process in 

 the shape of a wing behind the primary one, whether they belong to the abdominal 

 or the caudal portion. Syngnathus acus and röstellatus show hardly any pecularities 

 worth mentioning. 



In Nerophis the three anterior vertebræ are still immovably joined together, 

 but the third is more loosely attached to the second than in the genera Siphono- 

 stoma, Syngnathus and Hippocampus. In Nerophis œquoreus the greater part of the 

 dorsal fin Is situated on the abdominal vertebræ. In two specimens (Ç) 12 resp. 11 

 vertebræ are modified to this end, 8 belonging to the abdominal, 4 or 3 to the 

 caudal series; the groups of interspinous bones are the following: 



A: 6, 4, 4, 3, 4, 3, 3, 3 ] 4, 3, 3, 6 * 

 B: 4, 4, 4, 3, 4, 3, 4, 3 | 4, 4, 3. 



All the abdominal vertebræ are long, with stout transverse processes, distally 

 expanded and more directed downwards than in Siphonostoma, probably corre- 

 sponding to the more compressed shape of the body; besides, these processes are 

 somewhat nearer to the front end than in S. The first caudal has a well-developed 

 inferior (hæmal) arch; the last vertebra carries a single vertical plate, probably 

 * The three hindmost of the last group are densely crowded together. 



