300 GEOLOGICAL SURVEY OF THE TERRITORIES. 
they appear to be very hardy compared with the Branchipodide. The 
animals are pale flesh-colored, with black eyes, and are tolerably rapid in 
their movements, swimming often on their backs and rapidly gathering 
the vegetation at the surface with their antennz and either their coxal 
lobes or jaws. The eggs are carried upon the back under the shell, and 
are found in the spring. 
We have received numbers of the cast shells of the larva or nauplius 
from a correspondent at Hanover, N. H. The carapace bears a close 
resemblance to that of the nauplius of the European L. brachyura, hay- 
ing the lateral front spines and two small caudal spines. 
4 
LIMNETIS MUCRONATUS Packard. 
Plate I, figs. 1-6. (In fig. 1 the 1st antennz are not represented by the artist.) 
Limnetis mucronatus Pack., American Naturalist, ix, 312, 1875. 
Bulletin Hayden’s U. 8. Geological and Geog. Survey, iii, No. 1,172, 1877. 
Male.—Carapace much flattened, oval-triangular, the dorsal edge of 
the valve but slightly curved, the posterior end well rounded, while 
the front end is but slightly curved. Head in front truncate, much as 
in the males of LD. gouldii and gracilicornis, the end being broad and 
square. Hand large, a little longer than broad, with the claw large, 
and as long as the hand is broad; the lower edge of the hand (or 4th 
endite) armed mueh as in L. gouldii. There are twelve pairs of limbs, 
the twelfth ending in a pair of large, strong, recurved hooks. The 
end of the terminal segment on its ventral side is rather more pro- 
duced, and with a more conspicuous spine than in the female. - Two 
males occurred among forty-four females. 
The length of carapace, 4°"; breadth, 3.2™™. 
Female.—Carapace scarcely distinguishable from that of L. gracilicornis 
in outline, though it varies slightly in form, some being quite round 
and regular, others slightly ovate, and some quite flat and triangular. 
Muscular impression as in ZL. gracilicornis, but the muscular impression 
is much broader and proportionately shorter than in L. gracilicornis, 
where the front of the head is suddenly truncate, and wider at the 
extremity than behind in gouldii; while in gracilicornis it is also trun- 
= (cate, but does not contract so much in 
front of the eyes, the narrowest point be 
ing between the eyes and the end of the 
front. In the present species, however, 
the front is very much produced into a 
long, acute, mucronate point, with two 
teeth on each side, the middle tooth vary- 
ing much in length. The carina is very 
Fic. 2.—Lymnetis mucronatus, male; a high and sharp (see a in Fig. 3 in text). 
Gaw; both enlarged, 1st antenn® not 2d antenn with the second joint half as 
Grea ten Gel. long as the basal; the four succeeding 
joints very close, and together not as long as the succeeding seventh 
joint, from which arises the flagellum, the upper branch of which is 
14-15-jointed, the lower one 17-jointed, with ciliated hairs about as long 
as in D. mucronatus, the longest ones as long as the entire antenna. 
Twelve pairs of feet. 
The feet have a very long and slender flabellum, the gill being either 
in the first pair short and rounded at the end, or in the second and suc- 
ceeding ones long and pyriform, being about the same shape and size 
