° 
ENTOMOSTRACA OF MINNESOTA. PALA. 
The males have the opening of the vasa deferentia in front of the 
claws, which may be absent; the antennules are also modified, being 
longer and curved. In Lathonura the abdomen is elongated posteriorly 
till it begins to suggest a transition to Polyphenwus. 
The known genera and their distribution is as indicated below. 
Half of the known species are found in America, one-fourth being 
peculiar to it. 
peu) eae nly in Total 
ENE. ueclee, BoroneaE Amer:can. | hens American. 
| 
MIACTODATIXssicsccse cece eee base deus eee 4 3 2 1 3 
PALOMITAS ss ccwrcinas scieeine sees stssiaes 1 1 De SualliacsteWoroncees 1 
REMAN OGL s2i502 a0 sce ces vecmesocacs il Te Mg a RE es | 2a cecisiasiensclotell Woneescwuke tee 
MPTEMIOCCTHUS tor ssisncsscecelseetsioncedeese | 1 | Ly Thal Res ee crate | ancreeeteahes eters hie a oes tee 
Atcantholeberis:.::.5:.2c2+-, s0as-2ecsenl 1 Dee VN CTR social ai densi eee [tree meter eee 
ORVONUS ite vcthon ssa naevacne foceceecseowes i| 1 RA ante a wceche 1 
EVAN COC AP DMTAORE scot ccescelet cieosistie se 1 lirsntets Pesce alts dete estes 1 1 
UV OEY PLUS esse caseatines sese se naseeeees 3 | Ps Ball ects 1 1 
moe | Se ee 
700171 RO es Teh le 210 4 3 "i 
| 
GENUS MACROTHRIX Baird. 
Body oval, pointed behind; head broad; antennee of first pair long, 
nearly straight, beset with spines, olfactory threads terminal; swim- 
ming antenne large and powerful, propelling the animal by bounds; 
three jointed ramus with a greatly elongated sets which is thorned 
and jointed; labrum with the basal joint enlarged, resembling that of 
Iynceids; first foot with a hook in both sexes; last foot with a long 
process (respiratory body); abdomen short; claws short; caudal stylets 
often with a bush of hairs at tip. The intestine is straight and without 
ceca in front or behind. 
The first one to observe a member of this genus, apparently, was 
O. F. Muller whose Daphnia curvirostris is usually referred to Macro- 
thrix laticornis. 
The name Echinisca was proposed by Lievin, but Macrothrix was 
applied by Baird in 1843. Four species are known, three of which 
occur in America, and without doubt the fourth will ultimately be 
found. No males of this genus were known till 1877 when the male 
of M. laticornis was described and figured (Grube and Weismann ’80. ) 
Nearly two years later the male of VW. rosea was described from Wis- 
- consin by E. A. Birge. Descriptions of the male of Lathonura are also 
— given in both the above mentioned sources. 
5 14 
