244 THOMAS DWIGHT ON 



CLASSIFICATION. 



Class I. — Spines in which the number of praesaorals is normal, bnt in which there is 

 an irregularity (A) at the junction of the thorax and loins, or (B) at the junction of the 

 thorax and neck. 



Class II. — Spines in which the 26th is the fula'alis, but in which the 25th is not quite 

 separated from it. 



Class III. — Spines in which there are more than 24 perfectly free praesacrals: (A) 

 the extra one being thoracic, (B) the extra one being lumbar, (C) there being two extra 

 praesacrals, one thoracic and one lumbar, the latter sacralized on one side, the 27th being 

 the fidcralis. 



Class IV. — Spines in which one or more praesacral vertebrae are imjjerfectly de- 

 veloped : (A) one or more vertebrae being fused, (B) the atlas being fused with the 

 occiput. (C and D) the 24th being more or less sacralized. 



Class V. — Spines in which there is a praesacral too few : (A) a vertebra being 

 wanting in the loins, (B) in the back, (C) there being 12 pairs of ribs, the first pair 

 being cervical and perfect on one side, the 24th being in all groups the fidcralis. 



CATALOGUE OF THE SPINES. 



Class I. 



Group A. 615, G-19, 636, 567. 

 " B. 1, A-30, 649, 729, 306. 



Class II. 

 21, 561, 361, X, G-22, A-175, 2. 



Cl.vss 111. 



GR(.ri> A. 045, A-4, 764, 504, A-186, 578, 110. 

 " B. 4U3, Y, 381. 

 " C. 208, 297. 



