CRUSTACEA OF ALABAMA. n 



simple, 3-jointed ; abdomen in the female 3-jointed, in the male 5-jointed ; stylets in the 



female longer ; ova-sac single ; spermatophore pear-shaped, liable to be mistaken 

 for eggs. 



Pseudo-diaptomus pelagicus, Herrick. 



Final Report on Crust., Geol. Surv. of Minn., Vol. XII. 



Rather compact; thorax alike in the sexes, antennae short, seeming 22-jointed ; first 

 foot small, both rami 3-jointed ; fifth feet in the male with but small rudiments of the inner 

 rami, basal portion heavily armed with short teeth, otherwise almost as in Diaptomus ; 

 fifth feet of female slender, alike ; abdomen in male very slender, with short stylets 

 armed with five terminal setse and a series of bristles on the inner margins, distal margin 

 of segments of abdomen toothed ; a series of spines also ornaments the middle of the 

 first segment below; abdomen of female short and very spin)', first joint thick, second 

 slender, oblong, third joint short ; length of abdomen supplemented by that of the elon- 

 gated stylets, which are spinulous on the edges ; ova-sac ovoid, eggs numerous ; open- 

 ing of operculum vulvae with lateral projecting lips. 



This species is ornamented with irregular markings of brownish color which gives it 

 a strange appearance not observed in any other copepod. The size is like Temora velox, 

 which the female resembles a little, a resemblance enhanced by the elongated stylets. 



This genus affords an illustration of a " missing link" connecting the fresh-water 

 genus Diaptomus with its fellows of the sea. In most respects the species closely re- 

 sembles Diaptomus, while in others it approaches Drepanopus, and in still others Eu- 

 chseta. The entire reduction of the inner branches of the fifth feet in both sexes is espe- 

 cially remarkable in view of the three-jointed inner rami of all the other feet. The fifth 

 foot in the male is exceedingly like that of Drepanopus pectinatus, Brady, while those of the 

 female are on the same numerical plan ; in that genus, however, the male antenna is not 

 geniculate and the first foot has the inner ramus one-jointed. The genus Euchaeta is a 

 somewhat miscellaneous assemblage, with some species resembling Pseudo-diaptomus. 

 In some respects Centropages is likewise similar. 



Genus Diaptomus. 



Though the most abundant and widely distributed fresh-water genus of Calanidae, 

 our American species need careful revision. Pending such study, which must be based 

 on a painstaking study of the last stages of development, we can only say that at least 

 three species are found in Alabama, one being the D. sanguineus of Forbes, another, D. 

 stagualis, and a third, like D. pallidas, Herrick. 



