LAMPKEYS. 



69.' 



large numbers tlie rivers of Europe, Nortli America, and 

 Japan, and scarcely attaining a lengtli of two feet; the 

 " Pride " or " Sand-Piper " or Small Lampern (P. hranchialis), 

 scarcely twelve inches long, the larva of which has been long 

 known under the name of Ammocoetes. 



Ichtliyomyzon from the western coasts of North America 

 is said to have a tricuspid maxillary tooth. 



MORDACIA. — Dorsal fins two, the posterior continuous with 

 the caudal. The maxillary dentition consists of two triangular 

 groups, each with three conical acute cusps ; two pairs of serrated 

 lingual teeth. 



A Lamprey (J/, mordax) from the coasts of Chile and 



Fig. 317. — jMoTitli of Mordacia mordax, closed and opened. 



Tasmania. This fish seems to be provided sometimes with a 

 gular sac, like the following.^ 



Fig. 318. — Mordacia mordax. 



Geotria. — Dorsal fins two, the posterior separate from the 



^ Fig. 317 is taken from a specimen in which the horny covers of the 

 dentition were lost, hence it does not represent accurately the sliape of the 

 teeth. 



