BULLETIN OF THE UNITED STATES FISH COMMISSION, 197 



already assumed a horizontal position, the apparently scapular portion 

 is vertical; the pectoral rays seem to arise almost immediately from its 

 hinder border. A i)owerful azygos muscle originates from the anterior 

 border of the coracoids in the middle line which is inserted by a tendon at 

 the point of Junction of the hypohyal cartilages, as shown in the figure. 

 This muscle pulls down the hyoids and increases the capacity of the 

 tubular snout, and is one of the effective agents in the function of res- 

 piration; the muscle is represented in its contracted state in the figure. 



Structure of the unpaired fins. — These consist of the dorsal and anal. 

 The dorsal df has eighteen rays, which rest upon eighteen short inter- 

 mediary basal pieces, hc^ cartilaginous in structure, and which articulate 

 by a singular series of link-like structures with the cartilaginous inter- 

 spinous rays or basalia iCj nineteen in number. The muscles which 

 move the dorsal from side to side are arranged in eighteen pairs, and 

 run out radially and parallel with the interspiuous basalia, to be inserted 

 just where the intermediary pieces join the latter. In adult specimens, 

 the interspiuous basalia which are at this young stage nearly in contact 

 with the uotochord by their proximal ends, are pushed farther out and 

 become apjiosed upon and interposed between the spinous dorsal radii 

 springing directly from three vertebrae. The young, therefore, show 

 that the interspiuous basalia of the dorsal are at first more nearly in 

 contact with the vertebral axis. 



The anal fin, «/, just behind the vent v. has four distal radii unseg- 

 niented and hyaline, the same as those in the dorsal, nor are they yet 

 barely more than incipieutly cartilaginous in either of these fins. These 

 rest upon four short cartilaginous intermediary pieces, with the same 

 link-like articulations with the interspiuous basalia as were noted in the 

 dorsal. The interspiuous rays of the anal ic are three in number, and 

 are curved towards and nearly in contact with the notochord at their 

 proximal extremities ; but in the adult, as the abdomen develops, these 

 are pushed outwards, and between their inner ends and the vertebral 

 axis there is finall}- a wide interval. 



The brain. — Of this there is little to remark, except that its under 

 surface has a direction at right angles to the course of the upper end of 

 the medulla spinalis or spinal cord. The eye is relatively farther for- 

 ward, as. compared with the usual position of the cerebrum ce. The 

 eyes on this account are also more api)roxlmated than usual, only a 

 very thin interorbital septum separating them, behind which the 

 cerebrum terminates. 



Alimentary canal and appendages. — The oral cavity is disproportion- 

 ately prolonged on account of the length of the intermediary elements 

 of the lower jaw and the length of the trabecular rostrum, and extends 

 from the point m' to the pharynx or gill-chamber. The gill-chambers 

 communicate internally in the usual way by clefts with the pharyngeal 

 portion of the alimentary canal. They are essentially closed cavities, 

 except where the interbranchial spaces communicate with the throat, 



