438 Wisconsin Academy of Sciences, Arts, and Letters. 



extensive collections have been made in that state, but it would 

 seem probable that it must occur in many localities between 

 the Mississippi valley and the sea-board. 



In the description, as given above, the original description 

 is modified by the more complete knowledge made possible by 

 the study of a larger number of individuals. 



DiAPTOMUs siciLoiDEs Lilljcborg. 

 Plate XVIII, fig. 9. Plate XIX, figs. 4, 5, 7. 



1889. Diapionius siciloides Lillj., DeGuerne and Richard, p. 



54; pL I, figs. 7, 8, 28, 32. 

 1895. Diaptomus siciloides Herrick and Turner, p. 69 ; pi. 



VIII, fig. 10. 



1897. Diaptomus siciloides Schacht, p. 154. 



1898. Diaptomus siciloides Brewer, p. 125. 



1905. Diaptomus siciloides Pearse, p. 147 ; pi. XIII, fig. 5 ; 

 pi. XIV, figs. 7, 8. 



A small species. The first segment of the cephalothorax 

 about equals in length the three succeeding segments. The 

 last segment terminates in two lateral spines. 



The first abdominal segment of the female a little exceeds 

 in length the rest of the abdomen. It is expanded laterally 

 and in front, and bears two small lateral spines. The second 

 segment is considerably shorter than the third, and the third 

 and the furcal rami are about equal. The furcal rami are 

 ciliate on the inner margin. 



The antennae are 25-jointed and reach the extremity of 

 the furcal rami. The right male antenna is much swollen 

 anterior to the geniculating joint. The antepenultimate seg- 

 ment bears a hook which equals in length one-half of the pe- 

 nultimate segment. 



The first basal segments of the female fifth feet are armed 

 with the customary spines, and the second basal segments with 

 the usual lateral hairs. The exopodite is composed of two 

 segments, the third segment being represented by two spines. 



