FOSSIL AND RECENT 



173 



SO.S.C 



epo 



soc 



Fig. 88. Lebonichthys gracilis (Davis). Neurocranium in dorsal view. 

 Based on R.S.M. 1891.59.85 and 1881.5.36. 



The parietal is rhomboidal and meets its partner in a nearly straight median suture. 

 Between them the parietals cover much of the supraoccipital and the epiotics, only 

 the crest of the former and the processes of the latter being visible in dorsal view. 



The pterotic meets the frontal in a syndesmotic union, the path of the suture 

 line being due to the posterior margin of the frontal rather than the anterior border 

 of the pterotic which lies beneath the frontal. The posterior margin of the pterotic 

 is oblique and meets the lateral margin in a small laterally directed process which 

 marks the posterior end of the hyomandibular facet. The surface of the pterotic 

 is marked by fine ridges extending forwards from the centre of ossification. The 

 otic sensory canal ran in a deep groove incompletely roofed by bone. Posteriorly 

 the canal opened by a single pore at the level of the lateral prominence on the margin 

 of the pterotic. 



The anterior part of the neurocranium is defective in all specimens. The derm- 

 ethmoid is incompletely known but a median vertical ridge may be seen in several 



