CRUSTACEA. 
241 
generally large and well developed, and lies near to tlie anterior margin of 
the ceplialon, hut is always more or loss distant from the vertex of the 
helniet-like ceplialon ; it is very moveable, and furnished with numerous 
crystalline lenses. The antennae are formed differently in the male and 
female. In the female the first pair are conical and covered by the bealr, 
beyond which they protrude only to the extent of exposing a bundle of 
button-shaped hairs (‘^organs of touch ”). In the male they are cylindrical,, 
freely mobile, slightly curved at the base, and always united to the beak ; 
the free extremity, besides the brush of button-shaped hairs, carries a 
special flagellum, and on the anterior margin a delicate bristle or hair. The 
other pair of antennae, resembling those of Daphnia, are very largely de- 
veloped, and freely protruded. The peduncle of the same is multiarticulate 
near the base, and one of the small joints is furnished with two hairs. The 
outer of the two branches of the rowing-organs is three-jointed, and a little 
longer than the inner, which is four-jointed^. The number of jointed hairs 
attached to this appendage is variable. There are five pairs of legs [pereio- 
poda], which appear not to differ much from those of Daplinia. In the 
male, the last joint of the first pair is, as in Dophiia and Ceriodaphnia, 
with a hook and a long lash. The appendages of the plcon are three, but 
they appear to vary both in number and size in different species. The pos- 
terior portion of the pleon [postabdonien] reminds one both in form and 
movement of that of Dophnia, and when at rest is bent up under the pleon. 
At the caudal extremity exist two curved hooks ; and on the dorsal surface, 
behind the last articulation, on a small lobe stand two long finely plumose 
cilia. The anal aperture, which opens posteriorly to the caudal hooks, is 
surrounded by several small curved spines, Avllich increase in size as they 
approach the caudal extremity. 
Jlyalodaphnia haldhcrgicnsis, sp. n., Schddler, Archiv fiir Nat. I8G6, p. 18, 
tab. i. figs. 1-3, from Kahlberg. — J£. herolinensts, sp. n., Schridler, 1. c. p. 24, 
tab. i. fig. 4, tab. ii. fig. 8, tab. iii. fig. 16, from the Pldtzensee. — J£. {Daphnin) 
cucullata (Sars), Schddler, 1. c. p. 28, from Kahlberg. — IT. ccderstromii, sp. n., 
Schddler, 1. c. p. 31, from Kahlberg. — H. {^Daphnia) cristata (Sars), Schddler, 
L c. p. 29, from Kahlberg. — II. {Daphnid) longiremis (Sars), Schddler, Z. c. 
p. 30, from Kahlberg. 
Sida crystalUna (Miill.), Schddler, Archiv fiir Nat. I86G, p. 2, from 
Kahlberg. 
Daplmclla hmchyura (Lidv.), Schddler, /. c. p. 2, from IQililberg. 
Limoccphcdiis serndaius (Koch), and 6'. vctidus (Miill.), Schddler, 1. c. p. 2, 
from Kahlberg. 
Scapholeheris cornuta (De Geer), Schddler, 1. c. p. 2, from Kahlberg. 
Euryccrcus lamellatus, Schddler, 1. c. tab. i. fig. G only. 
Bosmina gihhcra, sp. li., Schddler, I c. p. 3G, tab. ii. fig. 9, and tab. iii. fig. 24, 
from Kahlberg. — B. rotunda, sp. n., Schddler, 1. c. p. 40, tab. iii. fig; 13, 
from the Pldtzensee. — B. longicornis, sp. n., Schddler, 1. c. p. 42, tab. ii. fig. 10, 
from the Pldtzensee. — B. longirostris (Miill.), Schddler, 1. c. p. 46, tab. iii. 
figs. IG-23,from the Pldtzensee. — B. (Lynceus) longirostris (Leydig), Schddler, 
1. c. p. 47, from Kahlberg. — B. londinensis (Baird), Schddler, 1. c. p. 48, from 
Kahlberg. — B. (^Monocidus^ cornuta (Jurine), Schddler, 1. c. p. 49, tab. iii. 
1866 . 
* In the figure they are both given as four-jointed. 
[voL. Ill,] R 
