Dr R. H. Tmquair on Chondrostens acipenseroides. 351 



is a rather small posterior frontal (p.f.). In no specimen 

 which I have seen are the plates in advance of the frontals 

 in sufficiently good preservation to enable one to map out or 

 describe them: the outline of the snout as given in the 

 restoration (Fig. 5) is therefore conjectural. Behind the 



vl J ' 





Fig. 1. — Cranial shield of a specimen of Chondrostens in the Museum of 

 Practical Geology, Jermyn Street. On the left side the displaced operculum 

 (o^.) is seen overlapping the post-temporal (p.^.) and outer supra-temporal {s.t. ). 



posterior marghis of the parietals and squamosals, and be- 

 tween these and the post-temporal elements of the shoulder- 

 girdle, is a transverse row of five small plates {s.t.). One of 

 these, of a rudely polygonal shape, is median, and placed just 

 at the union of the two parietals, and is flanked on eacli side 



