504 



MISS JOAN B. PROCTElt ON THE 



Skull. 



Differing from the common T. ihera in the following 

 particulars : — 



The praefrontals are larger than the frontals, and widely 

 separated from the post-frontal bridge; temporal and post -orbital 

 arches stouter in propoi-tion, especially the latter ; annuhis tym- 

 panicus larger, stapes as slender as a hair. 



Maxillary with three alveolar ridges, the inner one of which is 

 comparatively weak, the outer one, or maxillary edge, denticulate<l 

 with what appear to be minute pointed teeth of the acrodont 

 type, but which have not the composition of true teeth ; the number 

 is about 20 on each outer, and about 7 on each inner, maxillary 



Text-figure 13. 



Skull of adult (nat. size), a. Palatal view (horny sheaths not blackened), lb. Side 

 view (horny sheaths blackened). Hornj' sheath of maxillary partially dissected 

 away to show denticulations in the bone itself, c. Mandible (horny sheaths 

 blackened). 



ridge. One or two similar denticles between the cusps of the 

 prEemaxillary. These denticles are so fragile that if the adherent 

 horny sheath is removed in the usual way, they are completely 

 destroyed, but they can be clearly seen without a lens if the hoi'n 

 is partially removed. In text- fig. 13 this has been done, and the 

 remaining horn blackened in the profile view, in order to dis- 

 tinguish it from the maxilla. 



All the cranial foramina seem to be proportionately small. 



The mandible has both its alveolar ridges denticulated in the 

 same manner as the maxilla. In the figure the horny sheaths, 

 in this case entire, are blackened. 



Vertebrcd column. 



First eight (cervical) vertebrae as in T. ihera. 



The dorsal vertebrae (ninth to eighteenth in the complete 

 series) difi^^er profoundly from the ordinary pattern; they are 

 entirely without spinous processes and the centra are greatly 

 depressed instead of compressed, and hollowed to a thin shell 

 for the reception of the spinal cord, the vertebrae being thus a 

 simple depressed tube, adherent to the bony neural plates of the 

 carapace. In all other species the vertebral column is separated 



