as to be on a level with the ventral surface of the vertebral body. 

 The rib-carriers of the second and third vertebrae are thicker than 

 the others and distally are marked by a horizontal furrow (Fig. 3 Fr) 

 which foretells the future separation into ventral and dorsal portions 

 (Fig. 5). The sacral rib-carrier presents no variation from those pre- 

 ceding it. The rib-carriers from the second to the seventh or eighth 

 anterior trunk vertebrae have appended to them by fibrous tissue 

 rudiments of ribs. The first rib extends outwards and backwards 

 curving downwards and distally upwards to its termination beyond 

 the lateral nerve lying the depth of the vertebral body from the skin. 



Fig. 3. Atnphiuma larva 68 mm. 

 Camera lucida drawing. Section slightly 

 oblique to the transverse plane through 

 third trunk vertebral. The posterior pro- 

 jection of the neural arch in the preceding 

 vertebra (Fig. 2 pn) was destroyed. B-T 

 rib-carrier; N neural arch; Ir furrow in- 

 dicating two portions of the rib-carrier; 

 Art. V arteria vertebralis ; B ligament. J 



Art.v 



The size and direction of the second rib are the same as for the 

 first with the exception that the former terminates in an expanded 

 plate having a large hole in the middle. The double-headed character 

 of both ribs is indicated by a furrow at the distal end, which is not 

 prolonged proximally though the rib is flattened antero-posteriorly. 

 The remaining five ribs are much smaller diminishing posteriorly to 

 the seventh which is scarcely recognizable. No parostosis afiects any 

 of the ribs. 



A very significant feature is found in the string of cells forming 

 a ligament extending from the ventral side of the vertebral body to 

 the distal end of the rib-carrier (Fig. 2 acfl 3 B). The vertebral artery 

 lies between this ligament and the rib-carrier. The ligament is pre- 

 sent in all the vertebrae of the trunk and those of the anterior part 

 of the tail bearing rib-carriers. Its thickness ist greatest in the 

 second, third and last trunk vertebrae. The neural arches are as 

 represented by Dr. Field with the exception that the wide inter- 

 vertebral spaces are more nearly closed by a growth of bony lamina 

 on their anterior and posterior margins (Fig. 2 N). An interesting 

 fact in connection with this is presented in the posterior third of the 

 tail by the exit of the spinal nerves on one side through the middle 



