1874.] PROF. T. H. HUXLEY ON MENOBRANCHUS. 189 



otics behind, while, in front, the vomers underlie it on each side. Its 

 anterior extremity is truncated, and slightly concave forwards. 



5. The vomers (Vo) are much elongated, flattened, broader 

 behind than in front, and have a sigmoid curvature, which is 

 especially manifested by their inner edges. As the vomers come 

 into contact only by their anterior extremities, while their inner 

 edges diverge from one another backwards, there is left between 

 them a wide space, increasing in breadth posteriorly, which is occupied, 

 for the greater part of its extent, by the parasphenoid, but, in front 

 of the truncated anterior termination of this bone, by a part of the 

 chondrocranium. A series of teeth is set along the outer edge of 

 each vomer ; and its posterior excavated extremity articulates with 

 the palatine bone. 



6. The parietal bones (Pa) which are broad and flat, cover over 

 the greater part of the epiotic and pro- otic bones. They meet in a 

 median sagittal suture, which is about half as long as the whole 

 skull. Anteriorly, each parietal bone presents three processes. The 

 innermost of these (Pa 1 ) is the proper continuation of the bone ; 

 uniting with its fellow, it gives rise to the anterior half of the sagittal 

 suture, and extends forwards, as a long triangular tongue, which is 

 interposed between the two frontals (Fr). The second (Pa 2 ) and 

 third (Pa*) processes start from a common root. The inner, very 

 long and slender, runs along the outer edge of the frontal bone, 

 widening a little as it goes, and ends at the posterior boundary of 

 the olfactory foramen (I). The third process (Pa 3 ) is short, passes 

 downwards and outwards, and rests, in a manner to be described 

 presently, upon a cartilage connected with the suspensorium*. 



7. The frontal bones (Fr), separated behind by the conjoined 

 parietals, unite, in front, in a long frontal suture, and terminate, 

 anteriorly, iu pointed processes, which are received between the 

 ascending processes of the premaxillary bones. Between the latter 

 and the olfactory foramen, each frontal is continued into a plate of 

 bone (Fr 1 ), which lies on the sides of the snout. The anterior, 

 pointed, extremity of this plate fits in between the ascending process 

 of the prsemaxilla and the vomer, while its posterior prolongation 

 passes, below the olfactory aperture, to the cartilaginous antorbital 

 process of Jhe skull. 



8. A quadrate ossification (Qu) of irregular form, occupies the 

 distal end of the cartilaginous suspensorium. 



9. The palato-pterygoid (PL Pt) is a flattened plate of bone, 

 rounded and spatulate iu front, where it articulates with the exca- 

 vated posterior end of the vomer ; truncated behind, where it under- 

 lies the suspensorium. 



10. The prcemaxillee (Pmx). These are relatively strong bones, 

 each composed of a horizontal "body" boundiug the gape in front, 

 and of a strong ascending process, which passes back on to the top of 

 the skull, at an acute angle with the body of the bone. The " body " 

 tapers off to a point posteriorly ; and, in the specimen the skull of 



* Professor Owen considers that this process represents " the so-called 

 columella of Lizards" (I.e. p. 116). 



