426 



i\Ir. 11. Day on the 



slip;litly tluinb-bell sha[)ed in form — broad-basetl, then con- 

 stricting, to expand again and end in what appears to be 

 definite articulating facets. These anterior processes, 

 whicli are stout flattened rod-like structures, are to be 

 regarded as " basi pterygoid " processes, and are of great 

 interest on account of their articuhiting facets, tlie interest 

 of \vliich will be apparent when we come to deal with the 

 homologies of this bone. 



Cast of the dorsal surface of the compound para-basisphenoid bone of 

 Rhadinichthys mone^isis showiiiff the well-defined pituitary region. 

 (Specimen C.) X 76 diams. No. L 10822, M. M. 



The posterior pair of lateral processes are flat thin flanges 

 of bone whicii project outwards and backwards, and possess 

 on their surface a few indefinite ridges. 



This completes the account of the dorsal and ventral views 

 of the bone, but a few remarks may be added on specimen 0. 

 This is an almost complete cast of the dorsal surface of the 

 bone, only a i&w small fragments of actual bony material 

 being still adherent. The dorsal surface has already been 



