Rotator ia E 7 



The dorsal antenna is very large in diameter and obliquely truncate; 

 it bears a small tuft of sensory setae in a shallow, central depression. The 

 lateral antennae are in the normal position. 



The mastax, stomach, intestine, ovary and bladder are normal. The large 

 retrocerebral sac is slightly opaque at the posterior end and without any median 

 notch. 



The width of the median and lateral ribs or keels is variable, as shown in 

 figs. 3-5, plate 2. The lateral ribs usually project straight out from the body 

 or slightly downwards; the form with strongly upcurved ribs is not common. 



Total length 500-800 M ; length of lorica, 300-480^; width of lorica, 270- 

 430 M ; length of toes 90-140 M . 



This species has been known to the writer for some time from many locali- 

 ties in the United States; it was collected by President Birge, of the University 

 of Wisconsin, and Mr. Juday, of the Wisconsin Geological and Natural History 

 Survey, in ponds and bayous of the Mississippi river in southern Louisiana; 

 by Mr. Frank J. Myers, around Atlantic City, New Jersey, and in Polk county, 

 Florida; by Mr. Myers and the writer in sphagnum bogs and ponds throughout 

 Vilas and Oneida counties, Wisconsin. It was common in a collection made 

 by Jessup in lakes on Old Crow river flats, 40 miles north of New Rampart 

 House, on July 3, 1911. The presence of this species in the Arctic is of no special 

 significance, as the collections listed above show that it is widely distributed; 

 it seems, however, to be limited to regions with very soft, non-calcareous waters, 

 where it often occurs in great abundance. 



Euchlanis pellucida looks superficially very much like E. triquetra, but 

 it is considerably larger and readily distinguished from the latter by the absence 

 of the lateral sulcus. 



Euchlanis deflexa Gosse. 



This species, which is ordinarily considered quite rare, was common in 

 Jessup's collections: from a pond near Yukon river, Yukon Territory, May 26, 

 1911; pool at White Horse, Yukon Territory, June 7, 1911; lakes on Old Crow 

 river flats, 35 miles north of New Rampart House, June 23, 1911; lakes on 

 Old Crow river flats, 40 miles north of New Rampart House, July 3, 1911; two 

 lakes on Old Crow river flats, 55 miles north of New Rampart House, July 10, 

 1911; pools at Fort Yukon, May 24, 1912. 



Euchlanis triquetra Ehrenberg. 



Collected in abundance by Jessup in lakes on Old Crow river flats, 40 miles 

 north of New Rampart House, July 3, 1911; two lakes on Old Crow river flats, 

 55 miles north of New Rampart House, July 10, 1911; pools at Fort Yukon, 

 May 24, 1912, and in a slough of Old Crow river, near New Rampart House, 

 August 7, 1912. 



Euchlanis eoropha Gosse. 



A few specimens of this comparatively rare species were collected by 

 Jessup in lakes on Old Crow river flats, 40 miles north of New Rampart House, 

 July 3, 1911, and in a small muddy pool 25 miles north of New Rampart House, 

 July 17, 1911. 



Lecane ephestra, new species. 

 Plate 3, figs. 1, 2. 



The outline of the lorica is slightly ovate; the anterior margins of the 

 dorsal and ventral plates are coincident and straight. The anterior spines 

 are very short and rather stout. The dorsal plate is broadly elliptic and rounded 

 posteriorly; it is without markings. The ventral plate is considerably narrower 



24058 2i 



