170 



RECORPP OF THK ACSTKAIJAX MTSECM. 



Tlie upper jaw is nicked at the tip in _vonn<): spei-iineiis, l)ur 

 it gets Lfradually slmllowei" with age. Owing to tliis A-sliaped 

 bay the biting edge presents a sliglitly sigmoid curve. Lowei' 

 jaw with tlie horny sheath produced at tlie tip into a rather 

 strong, hooked, beak-like process. Xot sei'rated in the vouiii^-. 

 or onlv faintly so. 



p'ii>. 40. — Oie/n>/ia drfii-f.'.ui, Oinm. Lateriil ami (.(orsal views of the 



head of the type specimen of Xalator tesscl/atiis, .McCiiIl. (SpL-ciiiion 



No. 6 enlarged). 



The head dift'ei's mainly from that of ('. >injiJit>; \\\ tlu- foMow- 

 ing points: — Tlie prjefrontals do not for-iii a suture anttMiorlv 

 with the maxilliary sheath, and are not longer than the 

 supraocular. Tliere are only thi-ee instead of four oi- live 

 post(KMilar scales. The j)ost-parietals are never symmetrically 

 paired, being undivided or three in number. Areola^ present 

 in the young. 



Cn-'iji'irr (tigs. IL'-U): — Slightly archrd, broadly oval 

 but never shield-shaped, only slight I v nai'i'owcr lichirul 

 than in front: lateral edges refiexcd : sti'oiiglv scrratrd and 

 sjiined in the specimens in which areola' persist, but less 

 strongly Herrated in the oldest specimen. in traiis\erse section 

 the carapace presents the lines of a bow. Nucha! slightly 

 emarginate in very young e.vamples but vei-y deeply concave 

 in the oldest specimen ; paired in three out of the ten 

 specimens. Marginals sti'onglj- I'eHe.xed in the ohlest specimens, 

 but defle.ved in the vounger ones ; in twelve pairs, the first of 

 which are rarely in contact with the first vertebral shield ; 



