FAMILY STURIONIDiE ACIPENSER. 347 



central rays longest ; its tip reaching the lower base of the caudal. Caudal fin with its upper 

 lobe elongated. 



Color. Dark olive-grey above, occasionally brownish ; beneath light ash-grey. Fins often 

 red from infiltration. Pupils black ; irides golden yellow. 



Length, 18- 0. 



Fin rays, "D. 38; P. 28; V. 24; A. 23; C. 125" {Lesueur). 



This species appears to grow to a larger size than the preceding. The greatest differences 

 in the characters of the old and young appear to consist in the variable number of the tuber- 

 cles. It would belong to the genus Helopes of Brandt, which is thus characterized : " Snout 

 " long (one sixth or seventh the length of the body), and body covered with strong bony dis- 

 " tant shields." It forms a palatable food. 



(EXTRA-LIMITAL.) 



A. transmo7itanus. (Richardson, 1. c. p. 278, pi. 97.) Profile shelving off suddenly before the nos- 

 trils, into the greatly depressed and slightly upturned, moderately acute snout, which, measured 

 from the orbits, is y'^- of the total. Columbia River. 



A. rupertianus. (Id. 1. c. p. 311, pi. 97.) Snout narrow, not acute; its sides flattened; its vertical 

 height equal to half the transverse breadth. D. 40; P. 40 ; C. 112. Length two feet. Northern 

 Regions. 



A. maculosus. (Lesueur, 1. c. Vol. 1, p. 393.) Snout much elongated. Color reddish olive, with black 

 spots. Length six to eighteen inches. Ohio River. 



Genus Platirostra, Lesueur. Jaws, tongue and throat without teeth. Snout long, flattened and 



spatuliform. Body without plates. Tail only covered on each side by small bony plates. 

 P. edentula. (Lesueur, Ac. Sc. Vol. 1, p. 228; Say, App. Long, p. 254.) Snout not so long as 



one-third of the body, dilated and rounded at its end. Opercle long and pointed. D. 58; P. 26 ; 



C. 15.84= 99. Length three to four feet. A specimen in the Albany Institute, from Juliet, 



Illinois. 



