Birge—Notes on Cladocera. 
1033 
it would be at once necessary to divide the new genus into 
two sections corresponding to the two forms which were 
united. 
The discovery of this species makes it necessary to define 
again the genus Latona, as well as the two main species. The 
.genus has had, besides the long known species L. setifera (0. 
F. Mueller) only the very closely allied form L. groenlandica 
Wesenberg-Lund, differing chiefly in the shape of the appen¬ 
dix foliaceus, which is more elongated in the arctic form. 
This is perhaps entitled to rank only as a variety. The pres¬ 
ence of the hepatic coeca in L. parviremis requires us to omit 
from the diagnosis of the family Sididae the statement that 
these structures are absent. See Lilljeborg, ? 00, p. 15; Sars, 
’65, p. 21. 
Genus. Latona Straus. 
Body flattened. Head broad and blunt, rounded in front; 
‘small cervical sinus. Rostrum absent; the ventral surface of 
the head prolonged backward into a broad leaf-like expansion, 
somewhat tongue-shaped as viewed laterally, concave on its 
ventral surface. Fornices present but small; a thin lamella 
extends on each side from head to valves, projecting over 
base of antennae and mandibles. Antennules inserted on sides 
of ventral surface of head, well forward; their insertion 
partly covered by small fornix. Antennules stout and long, 
the shape differing in the two species. Antennae with very 
stout but not long basal joint; dorsal ramus 2'-jointed, its 
proximal joint with lateral expansion; ventral ramus 3-jointed. 
Valves sub-quadrangular; dorsal region flattened and nearly 
straight; posterior margin oblique to axis of body and convex. 
The whole free edge—anterior, ventral, and posterior—thickly 
set with long, movable, ciliated setae, each borne on a separate 
papilla. At the blunt point formed by junction of ventral 
and posterior margins is a cluster of very long setae, the 
longest often quite as long as the valves; these are frequently 
lost, leaving only the papillae to which they were attached. 
Valves not reticulated. Postabdomen stout, conical, covered 
by the valves, with small anal spines. Abdominal setae stout, 
