PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 395 



little columella {cl., Fig. 1), that lias its superior end abutting against 

 the under surface of the parietal, while its lower rests in a circular socket 

 intended for it, on the upper surface of the middle of the pt{?rygoid. Its 

 lower articulation is anterior to itsujiper, i. e., the bone leans backwards. 



In all of the American lizards that I have examined this bonelet is 

 constant, and Professor Huxley tells us in his Anatomy of Vertebrated 

 Animals, page 219, that "In the principal group of the Lacertilia., a 

 column-like membrane bone, called the columella (but which is not to 

 be, by any means, confounded with the stapes, to which the same name 

 is often applied in reptiles), extends from the parietal to the pterygoid 

 on each side, in close contact with the membranous or cartilaginous wall 

 of the skull. Hence they have been called '■'■Kionocrania''' or "column 

 skulls." 



Through this open space we also have lateral views of the pterygoids 

 and the basisphenoid with the parotic and pro-otic bones above and 

 immovably articulated with the latter. There seems to be a small sepa- 

 rate ossification wedged in between the squamosal and parietal behind, 

 articulating with the exoccipital and os qiiaclratum, that seems to corre- 

 spond with Professor Huxley's pteroUc. In the dried skull it is not 

 movable. 



The orbit is bounded by three bones: above by the frontal, as already 

 described; anteriorly by the lacrymal^ that articulates with the jugal by 

 a descending i^rocess, anteriorly with the maxillary, nasal, and frontal ; 

 while the posffrontal and jugal bound its posterior ,, 



moiety, the former bone articulating above with 

 the frontal and parietal, below and posteriorly with " 

 the jugal and squamosal, and the latter, the ju/jal, ^^^ "" 



by its anterior process with the lacrymal, by its 

 posterior with the postfrontal and squamosal ; thus 

 we see that the orbital periiihery is comj^lete. The 

 skull is completed laterally by the maxUlary ; this vp - 

 bone bears teeth in its alveolar process below, articu- 

 lating with the bones that go to form the roof of the 

 mouth internally, while, upon the aspect of the 

 skull we now have under consideration, it articu- J'i^z^. 



lates behind with the lacrymal and jugal, above with the nasal, ante- 

 riorly with the premaxillary. 



The prefrontal fulfills its customary function in constituting in part 

 an osseous septum narium, meeting the ordinary segments as they are 

 arranged in the Lacertilian skull. 



Passing to the base of the cranium (Fig. 2), we find the l)asisphenoid 

 giving off, near its anterior termination, or the base of the rostrum in 

 some vertebrates, on either hand, well-developed ptcrapophysial pro- 

 cesses that have dilated extremities to articulate with longitudinally- 

 elongated facets upon the pterygoids. These latter bones form one of 

 the principal features of the basis cranii ; they extend backwards, con- 



