74 



been justification as the 5th feet of both the female and male 

 as figured by Herrick ('87, pi. 1, fig. 4; pi. n, fig. 9) show minor 

 diflferences from the type, while the figure of the animal itself 

 seems to have been drawn from a compressed alcoholic specimen 

 and thus naturally distorted. 



The writer has had under observation, forms from Lake Pont- 

 chartrain, the artificial ponds (brackish) in Lower City Park, 

 New Orleans, and from the fresh-water ponds in Audubon Park, 

 New Orleans, and a critical examination of the diagnostic points 

 has led him to the conclusion that our form agrees with the type, 

 with the exception that they are somewhat smaller (averaging 

 .69mm for the female and .54mm for the male) and that the 

 furca of both sexes are somewhat longer in proportion to width 

 than in the European specimens. The latter average in length 

 1.5mm for both sexes. In our form, the small spine (omitted by 

 Herrick) between the two apical spines of the 5th feet of the 

 female, as figured by De Guerne and Richard from European 

 specimens, has been found in specimens from all localities. 



The species seems to have a wide range, being very common in 

 North European waters and recorded from the Caspian Sea, but 

 so far as the writer is acquainted with the literature it does not 

 seem to have been recorded south of the Gulf. 



From an economic point it seems to be quite important, con- 

 stituting at some seasons the almost exclusive food of the shad 

 in the Rhine and of the herring in the Baltic. The record from 

 the Audubon Park ponds tends to prove the conclusion arrived 

 at by European investigators, that it is equally at home in abso- 

 lutely fresh as in brackish waters. 



7. Labidoccra sp. A few female specimens of a fairly large 

 size (2.60mm) were secured from the plankton which seem to 

 break away from the described species of this genus. The 

 species approaches L. nerii (Kroyer) in the abdomen being 2- 

 segmented and the genital segment symmetrical. It also comes 

 near to L. nerii in the presence of 3 spines to the apical joint of 

 the outer ramus of the 5th foot, but is without the minute spines 

 on the outer margin as in that species, while the inner ramus is 

 prolonged into a symmetrical and rather robust acute tooth in- 

 stead of into an asymmetrical short and knob-shaped process as in 

 L. nerii. The genital opening is central, while in L. nerii it lies 

 towards the left side. In the wing-shaped lateral prolongations 

 to the last thoracic segment it is similar to L. nerii. 



The form also approaches near to L. aestiva Wheeler, in the 

 symmetrical genital segment and position of the genital opening 



