402 THE FKKSII-WATKU FIS1IKS OF EUROTK. 



operculum are less developed, the lower lobe of the caudal fin is absent, and 

 many of the later rays of the fin, which afterwards become jointed, are still 

 undivided. The pectoral, dorsal, and caudal fins are black at their bases, and 

 yellowish-white at their edges. 



The females have the snout rather blunter and longer, and the males are 

 distinguished by their olive-brown colour. 



Acipenser naccarii (BONAPARTE). 



Small Sturgeons are met with in the Adriatic which belong to this species. 

 They reach a length of three feet, but are more frequently about twenty inches 

 long. Acipenser naccarii goes up the river Po in May, and though never 

 abundant, supplies the markets of Milan and Pavia. It is found in the autumn 

 in the lagoons of Venice, where it is generally small. The Italians have no 

 special name for it, and it is termed Storione, in common with the other species. 

 Its colour is blackish-brown above ; the shields and under side are dirty white. 



At the base of the pectoral fin the body is higher than broad, the height 

 being one-ninth of the total length. The length of the fish is four and three- 

 quarter times the length of the head. Seen from above, the outline of the 

 head is lanceolate (Fig. 192). 



All the shields covering the head are finely rayed, regular, and closely 

 packed together. The temporal shields are short and narrow, rather smaller 

 than the epiotic shields, and much smaller than the frontal. The parietal 

 shields are long, notched behind to receive the broad heart-shaped supra- 

 occipital, and tapering in front, where they are notched to receive the small 

 anterior division of the ethmoid which separates the frontal shields. The 

 post-frontal forms the upper border of the orbit. In front of the frontal are 

 the pre-frontal, nasal, and other ossifications. The anterior end of the snout is 

 only partly covered with small irregular little plates, and shows a row of large 

 pores on each side running from in front of the nares forward to the end of the 

 snout. These pores are connected with the cephalic canals. The first dorsal 

 shield is broad. The mouth is large, but its breadth is not so great as the inter- 

 space between the eyes. It is placed in the middle of the length of the head. 

 The distance between the outer barbels is equal to their distance from the point 

 of the snout, but this breadth is less than the interspace between the anterior 

 nares. The barbels are nearly equally long, and do not reach back to the mouth. 



The number of dorsal shields varies from eleven to fourteen. The first is 

 slightly the largest, and its anterior extremity is received in the notch at the 

 back of the supra-occipital shield. The succeeding four or five shields are 

 as broad as long, but towards the dorsal fin they become relatively longer, 



