Fish of the Family of Sturgeons. 273 



sponding to the gill-openings, and one central posterior notch 

 of a triangular form. Each of the clavicles is provided with 

 numerous small ridges, of which one, longitudinally passing 

 through the centre of the clavicle, projects beyond the rest. 



The body gradually becomes thinner behind ; at the same 

 time, in the whole of its length, the vertical diameter remains 

 equal to the transverse diameter. The five rows of scutes 

 which pass along the body render its shape a little angular. 

 The extreme end of the tail, from the dorsal and anal fins, is 

 entirely covered with scutes, but much shorter than in Scaphi- 

 rhynchus Rafinesquii. The trunk of the tail of our Turkestan 

 species (i. e. the distance from the end of the anal fin to the 

 base of the caudal) is scarcely one seventh of the distance from 

 the front margin of the clavicle to the base of the caudal, whilst 

 the trunk of the tail of the American species is not less than 

 one fourth of the above-named distance. The distance from 

 the base of the caudal to the anus of the former species is to 

 the distance from the anus to the front margin of the clavicle 

 as 2 : 3, whilst these two distances are almost equal to each 

 other in the other species. 



Down the dorsal ridge, from the neck to the base of the 

 dorsal fin, there is a row of saddle-like scutes, numbering from 

 seventeen to eighteen ; they are closely set, and each of them 

 is supplied with a projecting longitudinal crest ending behind 

 in a sharp hook. The first scute, immediately adjoining the 

 occipital shield, is the largest of all, and of an irregularly tri- 

 angular form ; the second is smaller and shorter than all the 

 rest following it, which, again, gradually become larger and 

 longer than wide. Likewise also the crests become gra- 

 dually higher and their terminal hooks longer. The base of 

 each of the scutes is concave. 



The lateral rows of scutes commence from the suprascapulary, 

 extend to the base of the caudal fin, and consist of from forty- 

 two to fifty-seven pieces ; they are tolerably closely set, and 

 have an irregular obliquely rhomboid form, with a longitudinal 

 projecting crest along the centre. The crests of these scutes, 

 as the crests of the dorsal scutes, terminate in acute spines. 

 At the base of the posterior end of the shoulder-blades there is 

 a small hollow place. The scutes of the side rows, from the 

 first to the fifteenth (approximately) , gradually get larger, then 

 for a considerable space they retain almost the same size ; and 

 only those approaching the base of the caudal fin again gra- 

 dually diminish in size ; but they do not become so narrow 

 and flat as in Scaphirhynchus Rafinesquii. 



In each of the abdominal rows there are from seven to nine 

 scutes ; but it happens sometimes that in one row (sometimes 



