116 



The bodies of the vertebra; are long, lender, deeply excavated at both end*, and joined 

 together a* in the Sirfn lacrrtina. 



Presented by Prof. Owen, F.S.S 



Genus Axolotea. 



581. The cranium of the AxolotI (.Ixalotn marmoralmi). 



Tbe hainrci|>ital is represented by posterior prolongation of the common broad and flat 

 T basicranial bone which represetiU the bodie* of the cranial vcrtebrsr. Thr exooripitala are 

 separated below by the bastoccipital process, and abore by a thin drird cartilaginous repre- 

 seiiutirr of the sapcroccipital. Each rxoccipital derelopc* a mall, alniiMt flattened condyle. 

 anterior to which it is perforated by the eighth pair of nerves ; it articulate* abort with thr 

 parietal and ma*tiii<l, and U separated from the alisphenoid by the Urge cartilaginous pctro- 

 tal capsule, to which a (mall discoid representative of the sUpcs u attached, closing the homo- 

 logne of the ' feoestra ovali*.' The basiipliPiKiidal portion of the basicranial plate semis an 

 angular process outwards on each aide, which supports the aliiphenoid. Tin- surface* of the 

 alisphenoid are directed forwards and backwards, instead of from tide to side, and it consti- 

 tute* chiefly the anterior parietes of the otocrane ; the inner and anterior border it notched 

 by the great trigvminal nerve. The parietal* are long and broad, divided by the sagittal 

 future, and impreaaed at the posterior and outer angle by the anterior attachment of the 

 great doraal trunk-muscles. The mastoids are articulated to this part of the parietal and to 

 the cioccipitals, ami overarch the cartilaginous petroaals ; they give attachment to the tun 

 panic pedicle. The orbitoiphenoida are divided by a membranous tract of some extent from 

 the aliij.heooiiU, and articulate above with the extremity of the parietal, the frontal and pre- 

 fronlal bone*. There are neither paroccipitals nor postfrontals. The vomcrine portion of 

 the basicranial plate is chiefly cartilaginous. The nasal bones are very small, and separated 

 from each other by the junction of the premaxillaric* with the frontal*. Hie nasal pro 

 eeaae* of the premaxillaries are unusually long and narrow. The small maxillaries arc sub- 

 bifureate anteriorly, one part being attached to the palatine, the other to the premaxillary . 

 the rest of the bone extending backwards into a short and slender pointed proccM. The 

 alveolar border of both premaxillaricf and maxillaries iup|iorts a single row of small equal 

 and sharp-pointed denticles. Two bone* attached to the anterior and outer part of the basi- 

 cranial bone, and which may be regarded either as vomcrine or palatal, support each a nar- 

 row rasp-like group of minute denticles, which are continued backwards upon the beginning 

 of the pterygoid* ; the pterygoid* continued from the*e bones and from the tides of the basi- 

 cranial bone expand as they extend backwards and apply themselves to the inner ride of the 

 tympanic pedicle. A bristle is passed through the dried nasal meatus of the right side, show- 

 ing its posterior termination between the beginning of the pterygoids and the end of the 

 maxillary bones. Beside* the ordinary row of denticles upon the dentary piece of the lower 

 jaw, there U a second shorter series upon the splenial piece. 



Pretemted by Prof. Owen, F.R.S. 

 Q2 



