io FIELD COLUMBIAN 'MusEU>M ZOOLOGY, VOL. i. 



examined, the third arch has no corresponding axonost. The fourth 

 arch in one specimen has one lateral half articulated to the next axo- 

 nost, while the other half lies free behind the axonost. The fourth 

 axonost is loosely attached to the upper extremity of the fifth arch. 

 I find only four of these axonosts, but Franque figures seven, only one 

 of which appears to be closely connected with a neural arch. Others 

 lie between successive arches, as do two of them in one of my speci- 

 mens. Schmidt very incorrectly figures all the anterior neural 

 arches as being extended oiit into lateral halves longer than those 

 which succeed them. 



Between the lateral halves of each of the neural arches and 

 overlying the neural canal is found a pair of intercalated cartilages 

 (Fig. i, i. c.). These are vertebral in position, as is usually the 

 case with the bony fishes. In Lepisostcus Balfour found similar 

 masses of cartilages to be intervertebrally placed. Above these car- 

 tilages runs the superior longitudinal ligament. In the adults these 

 cartilages become more or less ossified, and the bony layer which 

 inve'sts each cartilage is continuous with that of the corresponding 

 half of the neural arch. 



As regards the lower arches, we find that those of the middle of 

 the tail are supported by the hypocentra alone, and the bases of these 

 arches lack a little of reaching the anterior border of the hypo- 

 centrum. In the posterior portion of the dorsal region the 

 transverse processes arise from the very hinder border of the verte- 

 bral bodies (Fig. 2). As we advance towards the head these trans- 

 verse processes are moved a little forward, until at about the middle 

 of the dorsal region they occupy a position near the middle of the 

 length of the vertebral body (Fig. 3). Near the head again 

 the processes appear again to be slightly nearer the hinder border of 

 the body. With respect to the level of origin of the pro- 

 cesses, it may be observed that at the anterior end of the vertebral 

 column they spring from the sides of the vertebrae halfway up. Fur- 

 ther back the processes slowly descend, so that those of the last dor- 

 sal vertebra arise from its lower side. In length these processes 

 increase from the first to the middle of the trunk, and then gradually 

 grow shorter to the last dorsal vertebral body. In the tail the lower 

 arches are joined to the centra by suture. Below the haemal canal 

 the lateral halves unite to form a spine. The spines of the first four 

 to six caudal vertebrae are articulated to their respective arches 

 just below the point where the lateral halves have united. The 

 elevated origin of the transverse processes in the dorsal region is no 

 doubt connected with the enlargement which that portion of the body 

 cavity has suffered. 



