312 



NORTHERN ZOOLOGY. 



radiated like the top of the head, but its under surface is quite smooth, without any plates on 

 the end of the subrostral bone or cartilage, which is slender and little prominent even in the 

 dried specimen. There are four barbels situated rather nearer to the orbits or mouth than to 

 the tip of the snout. They are quite simple, tapering and smooth, except that their inner 

 surfaces are studded with papilla? like beads, in a crowded double series. The anterior mar- 

 gin of the orbit is exactly midway between the tip of the snout and first dorsal shield. The 

 shape of the operculum is somewhat different from that of A. transmontanus, and its surface, 

 instead of being reticulated, is marked with fine granulated lines radiating from its middle. 

 Mouth smaller than that of the Columbia River sturgeon. 



Shields in general not so much compressed as those of A. transmontanus. There are 

 thirteen or fourteen dorsal ones, including a spineless one incumbent on the dorsal ; the spines 

 of the others resemble those of the sturgeon just mentioned : there are also two flat shields 

 between the dorsal and caudal. The lateral shields, thirty-five in number, have less acutely 

 spinous ridges than those of A. transmontanus, but with more oblique, longer, and more 

 approximated lozenge-shaped bases. The abdominal shields, nine or ten on each side, are 

 smooth or even pitted on the apex, instead of being crowned by an acute spine-tipped ridge : 

 there are two large flat shields between the anus and anal, and two smaller ones fill the space 

 between that fin and the caudal. There are also in one specimen two small shields between 

 the ventrals, — one before the other. Integuments of the tail nearly as in A. transmontanus. 



Fins.— Br. 0; P. 40; V. 30 ; D. 40; A. 25; C. 28/84. The fins in general, but the 

 vertical ones especially, are smaller than those of A. transmontanus. 











DlMEI> 



SIONS. 













] 



nches. 



Lines. 







Inches. 



Lines 



Length from 



tip of snout to extremity of tail 



26 



6 



Length of rostral barbels 



. 1 



3 



ji 



91 



curvature of tail 



22 



6 



3J 



pectorals .... 



3 



6 



n 



J) 



end of dorsal 



20 



1 



3J 



ventrals 



. 2 







9} 



J? 



end of anal . 



20 



2 



)> 



attachment of ditto 



2 



2 



?J 



)5 



beginning of ditto 



19 



1 



39 



attachment of anal . 



. 1 



1 



yy 



)) 



beginning of dorsal 



18 



2 



J7 



its longest rays 



2 







if 



)» 



anus , 



17 



6 



» 



attachment of dorsal 



. 1 



10 



:? 



„ 



end of ventrals 



17 



2 



3? 



its longest rays 



1 



11 



?> 



s» 



beginning of ditto 



16 







» 



attachment of lower lobe of 







5) 



)' 



nape, including first dorsal 







caudal 



. 



. 5 



8 



shield 



. 



..... 



6 



7 



jj 



its longest rays 



2 



9 



)•> 



3) 



nape, excluding ditto . 



5 







?j 



attachment of upper lobe 



. 5 



6 



jj 



V 



pectorals 



6 







Breadth of pectorals .... 



2 







?* 



?J 



posterior edge of gill-opening 



6 







>> 



between nostrils, upper orifices 



1 



2 



s? 



)> 



edge of operculum . 



5 



10 



„ 



between eyes . 



. 1 



8 



J) 



i) 



temporal spiracles 



4 



3 



;) 



between anterior sub-orbitars . 



1 



11 



JJ 



» 



posterior edge of orbit 



3 



6* 



j) 



between temporal spiracles 



. 1 



10 



» 



v 



anterior ditto 



2 



11 



)? 



between surfaces of scapulars . 



2 



8 



J> 



3) 



posterior end of subrostral bone 2 



8* 



Circumference of body where greatest 



. 8 



6 



»> 



J) 



angle of posterior sub-orbitar 



3 



8 











Si 



5> 



superior nasal orifice 



2 



4 











