List of Crustacea Cladocera from Madison , Wis. 
38 ? 
Sida, Limnosida and Daphnella have short, fleshy knobs rather than 
hooks, and Latona is devoid of any special structure. Holopedium has 
n hook similar to that of Lcttonopsis but much longer, as is natural in 
that genus. 
The new hatched male has the copulatory organ in the form of a pair 
of small buds, which do not reach the adult form until after four or five 
moultings. The antennule of the young male differs widely from the 
adult form. It is short, lacks the appendix ciliata, and shows a distinct 
suture between base and flagellum. The latter is covered with long stragg¬ 
ling hairs. The whole structure closely resembles the female anten¬ 
nule. It is clear that the extension of the male antennule beyond the 
sense-hairs in the homologue of the flagellum of the female. 
RELATIONS OF THE GENUS. 
Sars was entirely justified in separating Latonopsis from Latona. While 
the structure of the two genera is quite similar in the female, the male 
differs widely from that of Latona. The antenna is more like that of 
Daphnella than that of any other genus, especially in the rami, while the 
great development of the base is like that of Latona. The antennule is 
peculiar and shows an intermediate stage between that of Latona and 
Daphnella , though nearer the former. In the male, however, the anten¬ 
nule is more like that of Sida than that of Latona. In the form of the 
body, the outline of the head, in the fornices, the position of the eye, 
eye-muscles and optic ganglion; in the heart; in the shape of the cara¬ 
pace, and the development of the setae of the carapace, it approaches 
Latona. It lacks entirely the peculiar development of the antenna seen 
in Latona and [the plate on the lower side of the head; while Latona 
lacks the development of the shell-gland, which Latonopsis shows. In 
most of the points of resemblance and difference between the two 
genera, Latonopsis is nearer the ordinary form of the Sididce , and it 
may be considered as connecting Latona with the other Sididce , but 
with many cross-relations to other genera. 
RELATIONS OF THE TWO SPECIES. 
L. occidentalis is very close to L. australis. Indeed, I am not sure but 
that they are really the same species. There are many points of minor 
difference, but the most tangible is the antennule, which is about twice 
as long in the American form. It must not be forgotten, however, that 
Sars’ specimens were hatched from mud, and it may be possible that 
specimens collected in their native waters will agree more closely with 
the American species. If the difference is constant, L. australis is nearer 
the ordinary type of the Sididce in the structure of the antennule. 
