418 ]yisronsin Academy of Sciences, AHs^ and Letters. 



speaks of it as in the entire Mississippi valley, but witliout 

 specifying definite locations, 



Scliaclit ('97, p. 146) says it is extremely abundant near 

 Havana, 111. I have found it in only one locality in Wiscon- 

 sin, — Heart lake near Marquette. I have also found it in 

 collections from Elk lake. Clay county, Iowa. From the south- 

 ern states I have found it from Missouri, Tennessee, Arkansas, 

 Louisiana and Texas. It occurs, too, in Lake Minnequa in 

 Pueblo, Colorado, and in eastern Nebraska, and the presump- 

 tion is that it occurs at intermediate points between the Rocky 

 mountain region and the observed stations farther east. So 

 it would appear that it is not only found throughout the Mis- 

 sissippi valley, but that it is pretty well confined to that vallev. 

 and much more abundant in the middle and southern part of 

 the region. 



DIAPTO]\lUS FKANCISCANUS Lilljcborg. 



Plate XXVI, figs. 7, IL Plate XXVII, figs. 1, 2. 



1889. Diaptomus franciscanus DeGueme and Richard, j). 48 ; 



ph I, figs. 12, 13, 34; ph III, fig. 23. 

 1895. Diaptomus franciscanus Herrick and Turner, p 58 ; pL 



VIII, figs. 12 and 16. 

 1897. Diaptomus franciscanus Schacht, p. 160; pi. XXX, figs. 



1-4. 



Rather large. Cephalothorax widest at the middle, the last 

 two segments confluent f.bove. The lateral lobes, seen from 

 above, are short and obtuse posteriorly, and armed on each 

 side with two small spines. The first segment of the abdomen 

 is about equal in length to the rest of the abdomen, is moder- 

 ately dilated in front, rounded at the sides, bears two small 

 lateral spines, but lacks lateral processes. The indications of 

 a joint — an imperfect suture — remain long after maturity in 

 the posterior part of this segment. The second abdominal seg- 

 ment is much shorter than the third, its test more delicate and 

 easily pushed together. The furcal rami are short, their leneth 



