404 THK F1;FS1I-\VATF.K FISHES OF KUKol'F. 



Acipenser naccarii; variety nardoi (HKCKEL). 



A variety of the Adriatic Sturgeon, which does not differ in size or habit, 

 and is known only from the river Po and the lagoons of Venice, is characterised 

 by its yellow colour. With this are associated certain differences in the shape 

 of the head and forms of the cephalic shields. The relation between the 

 height of the body and its length is the same as in A. naccarii, but its thickness 

 is greater, being equal to the height ; and since the body is five and a third 

 times as long as the head it follows that the head is relatively shorter. The 

 outline of the snout is less pointed than in the type of the species, and the 

 length of the snout is equal to the breadth between the nasal apertures. The 

 shields on the upper part of the head have a strong general resemblance to those 

 already described, but there are some conspicuous differences (Fig. 193). 



The first dorsal shield is broadly pentagonal ; the epiotic shield is broad 

 and sub-quadrate, instead of oblong ; the supra-occipital terminates laterally 

 in sharp angles, and its parietal sides are notched out angularly by the 

 parietals, so that the median portion extends farther between the parietals. 

 The parietal shields are long, and as they reach as far forward as the anterior 

 margins of the eyes they come nearer to the extremity of the snout, because 

 the eyes are placed farther forward, in this form than in A. naccarii. 



The sqtiamosal shields are broad and participate in the elongation. The 

 post-frontal are more decidedly triangular ; the frontal more decidedly lozenge- 

 shaped, while the ethmoid ossifications are small, three or four in number, and 

 penetrate far between the parietals, though not reaching quite so far back as do 

 the frontal shields. In front of these are pre-frontal, nasal, and other small 

 ossifications. There is a row of pores near to the anterior border of the snout, 

 which is otherwise covered with an osseous crust. The mouth is placed as in 

 A. naccarii, and the lower lip is not developed in the middle. The outer barbels 

 reach back to the month. 



The dorsal shields are thirteen or fourteen in number. The first is the 

 broadest, and the succeeding three or four are also broader than long, but 

 otherwise present no distinctive peculiarities. Two smaller median shields are 

 developed behind the dorsal fin. The lateral shields, forty in number, are twice 

 as broad as long and keeled in the usual way. There are ten ventral shields, 

 which are rounded and keeled. Two similar shields, rarely three, of which 

 the hinder is commonly the larger, are developed in front of the anal fin. A 

 small shield, without a keel, is placed behind the anal fin. The star-shaped 

 bony scales are developed over the skin, as in A. naccarii, and the lozenge- 



