are equally well developed in the anterior half of the tail, the last 

 one occurring on the twelfth vertebra. In every case this process is 

 invested with a thin parostosis except at the end where the cartilage 

 goes over into concentrically arranged cells of fibrous tissue. This 

 latter feature is as strongly marked in the tail as in the trunk. In 

 the trunk and the anterior part of the tail the cartilage of the neural 

 arch is quite continuous with that of the rib-carrier (Fig. 1) but the 

 cartilage of the latter six or seven rib-carriers of the tail is separated 

 from that of the arch by an intervening plate of bone as is shown by 

 GöPPERT in Menobranchus. The arteria vertebralis throughout 

 courses directly beneath the root of this process (Fig. 2). In all cases 



Fig. 1. 



Fig. 2. 



Fig. 1. Amphiuma larva of 68 mm. Camera lucida drawing. Transverse 

 section of second caudal vertebra slightly anterior to the middle. The fifth section 

 posterior to this shows the cartilage of the neural arch N dorsally in union, an lamina 

 of bone on anterior margin of neural arch. B-T rib-carrier (Rippenträger) ; Art. v. verte- 

 bral artery; H haemal arch; Ao aorta, Cv caudal vein. 



Fig. 2. Amphiuma larva 68 mm. Camera lucida drawing. Transverse 

 section of third vertebra anterior to sacral. The fourth section anterior to this shows 

 the cartilage /Vi and R-T in union laterally thus showing the neural arch in the middle 

 of the vertebra to be formed of m complete cartilaginous ring invested by a thin par- 

 ostosis. B-T rib-carrier; N posterior margin of the neural arch; pn posterior extension 

 of the neural arch; B a fibrous ligament of cells; Ch chorda; Art. v. ventral artery; 

 Cv ventral canal. 



the surface of attachment of the rib-carrier is in the middle of the 

 length of the vertebra and extends ventrally to a level with the middle 

 of the vertebral body. Figure 2 shows the attachment higher than 

 figure 1 as the former is through a more posterior plane of the 

 vertebra. The distal end in the anterior part of the body lies in 

 the same plane as the lateral nerve but posteriorly it sinks lower so 



