DEVELOPMENT OF THE SKELETON OF THE TUATABA. 



PLATE II. 



SPHEKODOX PUKCTATUS. VEETEBRAL COLUMN A5D BIBS, GASTEALiA, A5D TEETH. 



., arch of atlas ; ab. f , abdominal rib, median portion ; ab.", abdominal rib, lateral portion ; 

 c.au., auditory capsule; d., dentary; e.o., exoccipital; g.t., gastralia tissue tracts; i.p. 1 , median 

 intercentrum ; ip*, chevron-bone; m., costo-cervical muscle; .', ligament of costo-cervical 

 muscle ; mt., Meckel's cartilage ; ur., maxilla ; my., myelon (spinal cord) ; *.', first spinal nerve ; 

 njcii., twelfth cranial nerve ; n.a., neural arch ; nc., notochord ; nc.e., chorda! epithelium ; ncj., 

 chorda! sheath ; n.p., intravertebral chordal plate ; n*., neurocentral suture ; o.r.. osseous vertebra ; 

 p.a., pro-atlas ; px. y premaxilla ; r.c., cervical rib ; r.cd., caudal rib ; r*., sacral rib ; r./., trunk rib ; 

 /.a, interarticular tissue; txh., cheek-tooth; t.d., developing tooth; t.f., fully-formed tooth (fused 

 with bone) ; /.*., inner incisor ; /.*., middle incisor ; t.o., outer incisor ; /./>., transpalatine ; 

 u.p.j nncinate process. 



Fig. 1. StageS. Anterior cervical vertebra : The first five vertebrae showing anterior cervical 



ribs, lateral aspect. x 8. 



Fig. 2. Stage T. The game : The first 5-6 vertebrae showing osseous and so-called ligamentous 



cervical ribs from left side, ventro-lateral aspect. x 4. 



Fig. 3. Stage S. The "Pro-Atlas" : Lateral longitudinal section, including the exoccipital. 



x 20. 



Fig. 4. Stage S. The Ribs : Transverse section of last presacral vertebral segment. x 20. 



Fig. 5. Stage S. The game : Transverse section of the second sacral vertebral segment. x 20. 

 Fig. 6. Staff e S. The same : Transverse section of the fourth caudal vertebral segment, x 20. 

 Fig. 7. Stage R. Uncinate process : Section through a poststernal rib showing development of 



nncinate process. x 25. 



Fig. 8. Stage 8. Abdominal ribs : Ventral aspect of ribs 3-5. x 8. 



Fig. 9. Stage S. The game : Ventral aspect of ribs 16-18 of right side. X 1 1. 



Fig. 10. Stage T. The game : Ventral aspect of ribs 7-16 showing irregular union of parts, x 2. 

 Fig. 11. Stage R. Notochordal plate : Transverse section showing first origin. x 40. 



Fig. 12. Stage S. The same : Transverse section at full formation. x 25. 



Fig. 13. Stage S. Chevron-bones : Transverse section showing attachment to fourth caudal 



vertebra. x 25. 



Fig. 14. StageS. Incisor teeth : Front aspect. X 5. 



Fig. 15. Stage T. The same : Front aspect. X 4. 



Fig. 16. Stage T. The same : Median longitudinal section through second upper incisor and 



associated parts. x 23. 



Fig. 17. Stage T. Maxillo-palatine teeth : Combined drawing the teeth already confluent with 



the bone being indicated in outline, the developing teeth in colour. x 13. 



Fig. 18. Stage S. Cheek-tooth : Transverse section, including dentary and MeckeFs cartilage. 



x 20. 



