Mr. T. Atthey on Anthracosaurus Russelli. 157 



are difficult of definition, owing to the crushed state of the 

 bones. 



At -V inch behind the anterior margin of the bone there is an 

 oblique projection on each side of the middle line ; these are 

 ^ an inch apart at their anterior, and 1-jSg- inch at their posterior 

 ends ; and each is -^ inch long. A well-defined smooth and 

 deep groove or channel runs along the inner sides of their 

 bases from before backwards. 



The hasioccipital is 2| inches long by 1| broad at its posterior 

 part, and i an inch at its apex. It is articulated in front to 

 the basisphenoid, and on each side apparently to the quadrate 

 bone. The deep cavity behind for articulation to the body of 

 the first cervical vertebra is broken off obliquely near to its 

 posterior margin ; and the anterior part which remains is much 

 compressed. 



The occipital surface is IxV inch in depth from the posterior 

 borders of the so-called supraoccipitals or top of the skull to 

 the lower border of the hasioccipital. On the left side of the 

 median suture the bones are entire to near the outer margin 

 or angle of the exoccipital ,• on the right side part of the ex- 

 occipital is broken obliquely off, together with a part of the 

 epiotic and hasioccipital, exposing to view the sutures con- 

 necting these bones. The bone which I believe to be the true 

 supraoccipital is slightly overhung above and near to the 

 median line by the so-called supraoccipitals of Von Meyer, 

 and next by a small portion of the epiotics : it is united below 

 to the occipitals ; but its outline is not clear. 



The exoccipitals ^ united to each other on the median line, 

 form the sides and upper margin of the foramen magnum. 

 They unite above, first to the supraoccipitals, further out to 

 the epiotics, and below to the hasioccipital. This forms the 

 lower border of the foramen magnum; its lower border is broken 

 off below, as before noticed. 



The mandible. — Both rami are well preserved, and have 

 been separated from each other at the small loose symphysis, 

 probably in consequence of decomposition having been in an 

 advanced stage before the animal was finally enclosed in the 

 mud and its position fixed. 



The right ramus has been turned completely round, so that 

 its anterior end lies upon the posterior part of the right side, 

 and its posterior end upon the anterior part of the same side, of 

 the cranium. 



The left ramus has also been moved from its normal posi- 

 tion to the right side of the cranium. 



The symphysis of the mandible measures only | inch in depth, 



