294 



NORTHERN ZOOLOGY. 



middle of little circular depressions having a raised margin, which are partly concealed by a 

 rugose, tessellated plate, investing the inner surface of the lips, and of the same horny nature 

 with that which forms the outside of the teeth, — both are softened and peel off when the speci- 

 men is kept immersed in spirits. Four small, acute, conical teeth stand in a row across the 

 upper part of this plate, and four larger ones occupy each of its sides, the upper and lower 

 pairs being bicuspid, and the middle ones tricuspid : these stand on the sides of the maxillary 

 ring, or inner orifice, and have their ends turned towards it; the inferior margin of this orifice 

 is armed with a slightly-curved dental piece, having five acute points or teeth ; and opposite 

 to it, on the upper side of the orifice, is another piece, having two large, acutely-conical lateral 

 teeth, with a smaller central one. The tongue is also clothed with a horny-looking substance, 

 which is edged anteriorly by a row of about twenty fine teeth. 



The dorsal fins rise in even curves which are highest in the middle ; the first one is about 

 one-third of its own length distant from the second one, which unites with the caudal, the point 

 of junction being marked by a depression. A fold of skin becomes perceptible on the under 

 edge of the tail, a short way behind the anus, and gradually expands into the lower caudal 

 lobe towards the tip of the tail, where its height, in conjunction with that of the upper lobe, 

 equals the greatest height of the second dorsal. 



Colour. — " Back and sides bluish-grey with irregularly-scattered yellowish patches. Belly 

 yellowish-white." (Gairdner.) 











Dimensions. 













Inches. 



Lines. 





Inches. 



Lines. 



Length 



from tip 



of upper lip to extremity of 







Length of space between 1st and 2nd dorsal fins 1 







caudal fin 



. 



21 



6 



„ upper lobe of caudal 



1 



6 



V 



» 



end of second dorsal . 



20 



1 



Height of both lobes of caudal 







10 



3) 



r* 



anus .... 



15 



5 



„ first dorsal .... 







4 



„ 



» 



origin of second dorsal 



14 



11 



„ second dorsal 







10 



;> 



s> 



end of first dorsal 



13 



11 



Length of axis of mouth . 



1 



2 



3? 



„ 



origin of ditto 



10 



8 



„ its transverse diameter . 







9 



J* 



!) 



last gill-opening 



4 



10 



„ diameter of inner orifice of max- 







»> 



j> 



first ditto 



2 



8 



illary ring ..... 







5 



5' 



?» 



centre of eye 



1 



8 



Distance between the eyes . 







H 





of first dorsal .... 

 second ditto 



3 

 5 



3 



2 



Greatest circumference of body 



4 



6 



[125.] 2. Petromyzon fluvialis. (Linn.) River Lamprey. 



Petromyzon argenteus. Bloch, t. ccccxv., f. 2. 



Petromyzou fluvialis. Richardson, Frank. First Journ., p. 705. 



A lamprey having teeth like fluvialis was found in Great Slave Lake adhering 

 to an Inconnu (Salmo Mackenzie). It was very like Bloch's figure above referred 

 to, which Cuvier thinks is not different from fluvialis. 



