10 ACIPKNSER1M. 



with each other for a part of their length ; before the 

 coronals and between the eyes lie the frontal shields form- 

 ing another pair ; in the Frith of Forth Narrow-nosed 

 Sturgeon the frontals are wholly separated by one or 

 more interfrontal plates; the postfrontal and prefrontal 

 shields are exterior to the main frontals in the positions 

 that their names indicate ; laterally with respect to the 

 coronals lie the temporal shields, often coalescent with 

 a squamosal piece ; and behind them occupying the 

 posterior lateral angles of the head, and protecting on each 

 side a styloid process of the cartilaginous skull (which 

 Owen terms a representation of the par-occipital, but 

 which Kittary calls the mastoid), lies a shield that articu- 

 lates with the first dorsal, the occipital, and squamosal, 

 and the suprascapular : the last-named shield being the 

 first of the humeral chain that descends behind the gill- 

 opening, heads the lateral series of body -shields, all of 

 which partake of its scalene form ; the chevron-shaped 

 humeral shield gives support to the bony ray of the pec- 

 toral ; and the coracoid, the largest piece of the humeral 

 chain, has wholly a ventral aspect, its crest being on a line 

 with the crests of the ventral body-shields ; the supra- 

 scapular, opercular, and such cranial shields as have a 

 lateral aspect, are represented in the profiles of the head. 



The arterial bulb of the Sturgeons is furnished with 

 two rows of valves at its commencement, and with one 

 row at its termination. The swim-bladder is very large, 

 and communicates with the gullet by a wide hole. In 

 the glandular conglomeration of their pancreatic caeca 

 the Sturgeons resemble the Sharks. 



Heckeland Kner* divide the genus into six groups, three 

 of which, viz. the Lionisci, Acipenserini, and Helopes, have 

 the dorsal shields highest at their posterior edges, and the 

 * Siissw. Fische cler Ostreich. Mon. 1858. 



