234 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
long spines and aggregations of bristles and small spines; it is almost. 
round and enormously enlarged. The intestine is coiled and expanded 
at the end but the anal cecum is rudimentary. The antenne are 
heavily spined and have eight sete; the labrum is more or less hairy. 
The male has a strong hook on the first foot, and between the terminal 
claws of the abdomen is a peculiar intromittent organ. 
* Leydigia quadrangularis Leydig. 
PLATES LIX, Fic. 6; LX, Fia. 4. 
Lynceus quadrangularis—Leydig, Fric. 
Alona leydigii—Schoedler, P. E. Mueller. 
The shell is comparable to that of Alona quadrangularis, but higher 
behind; the markings are not very distinct; shell transparent. The 
head is very small; the eye smaller than or of about the size of the 
pigment fleck. The post-abdomen is very broad, the posterior margin 
nearly the segment of a circle, armed with numerous very long unequal 
spines which extend only about half the height, being replaced by 
short close hairs; the anal opening is very high; the terminal claws 
are long, straightish, and have a small thorn near the base. 
The males are smaller than the females, and the abdomen is less. 
broad; the antennules are longer than the beak and furnished with a 
flagellum. The sexual period occurs in September or irregularly. 
This species has only been encountered once, during September, in 
Poplar river, Cullman county, Alabama. 
*Leydigia acanthocercoides Fischer. 
Lynceus acanthocercoides—Fischer, Leydig. 
Eurycercus acanthocercoides—Schoedler. 
Alona acanthocercoides—P. E. Mueller. 
Herrick. 
Leydigia quadrangularis 
This species, reported in a previous paper, is, aS was said, nearest 
like L. acanthocercoides; and I am now able to verify the very incon- 
spicuous differences upon which the two are separated. Our specimens 
of the L. quadrangularis have the pigment fleck fully as large as the 
eye, Kurz to the contrary notwithstanding, and the spine of the claw 
of the post-abdomen is present, while in the present species the pig- 
ment fleck is much larger and furnished with lenses; the spine of the 
claw is wanting; the labrum is densely hairy; the abdomen is narrower, 
and the shell higher. The shell is very obviously striped in the pos- 
erior portion. The anus is higher thanin the previous species. In 
ther respects the two seem alike. 
