40 



him at West Alton, Mo., in which a fifth of the number were 

 of this species. It is also said by him to occur, as a rule, in 

 swifter water than the common shoveluose. 



The following table exhibits some of the more important 

 differences observed in comparing our nine specimens of 

 P(ifasi-(ip/iii-/ii/iiclnis alhiis with twenty-one specimens of Scaplii- 

 rhiiiichiis pliilorliijiichiis in the Laboratory collection. 



p. a/li!is S. platoi-Jn nchus 



Ribs 20 or 21 10 ijr 1 1 



Ventral radials 9 7 



Gill-rakers (points) 2 or 3 2- 5 (usually 4 or 5 



Air-bladder in lengtli head and body 8 5 



Belly and breast naked fully armored 



,,.,,. . scattered , . 



Sides between scuti s -r .- 



ossihcations 



Depth lateral scutis in length head and body ... . 28—32.5 10.8— 23.8 



Eve in interorbiial space 8.3—10 5-3— 8-3 ("Siially 



' ■' less than 71 



Inner barbel in outer 1.7 — 2.q i.i— 1.4 



Width mouth in width snout 1.4 — 1.6 1.6 — l.q 



Width head in length head 2.5 — 2.q i.q — 2.2 



Length head in length liead and body 2.9 — 3.2 3.5 — 3.8 



The first of the shovelnose sturgeons was descrilted in 1S20 

 by Rafine.sque as Acipcnst'i- plnforlnjiicliKs, and was. in 1S35, 

 made by Heckel the type of a new genns distinguished from 

 Acipoisvr by the absence of spiracles. The first of the Asiatic 

 species was described by Kessler from the Suir-dar in 1872 as 

 S. fedfscJieiiL-oi ; the second, »S'. k(ii(fin<iinii. by Bogdanov in 1875; 

 and the third in 1877 from the Amu-dar as 6'. henna mii by 

 Kessler, who also discussed and figured Bogdanov's species. A 

 fourth species was described by Nikolsky in 1900 as the type of 

 a new genus, PsciKloscdphirlnjnchHs. Berg ('O-l) unites the three 

 preceding specie.s under this genus, but does not recognize 

 Nikolsky's species as distinct. 



The American and Asiatic species were first subjected to 

 detailed anatomical analysis by Brutzer ('59) and Iwanzow 

 ('87), the memoir of the latter being our fullest treatise on its 

 subject. Zograft' wrote in 1887, and again in 1896, especially on 

 the embryonal teeth of these and other cartilaginous ganoids- 



