154 MARINE AND FISHERIES 



5 GEORGE v., A. 1915 



Stomachs of whitefish, Lake Superior (Smith), and of herring, Clupca aestivalis, 

 in Lake Ontario (C). 



The identification of the Mysis of our lakes with that occurring in the Scan- 

 dinavian lakes seems at first sight very surprising. It is impossible for it to have 

 been transported from one place to the other. This makes it practically certain 

 that they have both been derived independently from one of the marine species, 

 probably Mysis oculata. Smith, after comparing the American with European 

 specimens, states that he is unable to find any differences. I have had no European 

 specimens for comparison, but a comparison with Sars' account (1867), has shown 

 me no differences, with the possible exception of the third and fourth pleopods 

 of the male. But as these appendages differ in different individuals from our lakes 

 and as the figures of Sars are evidently from a somewhat immature male, I hesitate 

 to ascribe any importance to the differences noticed. A careful study of an abun- 

 dance of material may yet show that our species is distinct from the European. 

 Length about 16 mm. 



Order DECAPODA. 



The forms belonging to this group are larger than those of the other groups. 

 There are a single shrimp and eight species of crayfishes from the region of the great 

 lakes. 



Key to the Genera. 



Ai Third from last pair of thoracic limbs not chelate (provided with pincers). 



Palaemonetes. 



A2 Third from last pair of thoracic limbs chelate Camharus. 



Palaemonetes paludosa (Gibbes). Fig. 7. 



Hippolyte paludosa Gibbes, 1851, p. 197. 



Palaemonetes exilipes Stimpson, 1871, p. 130; Smith, 1874, p. 641. 



Palaemonetes paludosa Kingsleyi 1878, p. 97; Underwood, 1890, p. 374. 



This is our only large shrimp. It is found swimming about in the bays and 

 rivers of the Lake Erie drainage area. It has not previously been recorded from 

 Canada. 



Fig. 7. 



Localities. — Detroit River and Sandusky Bay (Lake Erie) (Smith). 

 Welland River (Wa). 



Stomachs of Perca flavescens, Apomotis cyanellus, and Ameiurus natalis 

 (Forbes, 1888). 



