156 Mr. T. Attliey on Antliracosaurus Russelli. 



Since the paper on Loxomma appeared, I have met with a 

 similar occurrence of two teeth in the right vomer of that 

 Labyrinthodont. 



The pterygoids are long bones united in front to the vomers ; 

 and if the skull had not been so severely crushed, they would 

 probably have been seen united by suture along nearly the 

 whole of their inner margins. As it is, they have been dis- 

 located ; and their well-preserved margins can be observed 

 pressed up to the level of the upper edge of the presphenoid, 

 which projects between them on the median line. By their 

 outer borders they articulate with the palate and jugal bones 5 

 and their posterior margins form the anterior and inner borders 

 of the supratemporal arches. 



The presphenoid is a long narrow ridge of bone on the 

 median line, extending forwards from the anterior end of the 

 basisphenoid, to which it is united by a transverse suture for 

 seven inches. It is articulated above to the under surfaces of 

 the nasals and frontals ; from the posterior end of the upper 

 border, \\ inch in depth, an ascending process on each side 

 passes up to the under surface of the parietals. Its inferior 

 margin is, for two inches posteriorly, rounded off; it is there 

 nearly | incli in width ; and the anterior end of the bone is 

 -V inch in width. At the distance of half an inch from its 

 posterior end the bone is fractured longitudinally for 2| 

 inches. At three quarters of an inch from its upper border 

 the lower half inch is pressed up above the upper. The two 

 halves, when united^ are 1;^ inch in depth. The bone at this 

 fracture measures -^ inch in breadth. For two inches in 

 front of the fracture the presphenoid is perfect, and is 1 inch 

 in depth ; and from this point to the anterior end it rapidly 

 diminishes to y^ inch in depth, as above stated. 



From under the inner margins of the above pieces, which 

 have been widely separated, there curves inwards and back- 

 wards, on each side, a short strong piece of bone, which ends 

 in a truncated extremity that is somewhat concave. These 

 bones are very distinct, difficult of determination, and may have 

 been for muscular attachment or osseous articulation. Their 

 ends are parallel with the suture connecting the pre- with the 

 basisphenoid. 



The supratemporal or pterygoid arches, as seen from below, 

 are 2| inches in length, by about 3 inches in width, bounded 

 anteriorly and internally by the pterygoids, externally by the 

 quadrate-jugal, and posteriorly by the quadrates. 



The hasis2)henoid is united in front to the posterior margin 

 of the median ridge or presphenoid, and behind, by a trans- 

 verse suture, to the apex of the basioccipital. Its outer borders 



