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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume VIII (1888-1891)

Birge, Edward A.
List of crustacea Cladocera from Madison, Wisconsin ,   pp. 379-Plate XIII ff. PDF (7.9 MB)

Page 393

        List of Urustacea, Oladoera from Madison, Wis.        393
-very small teeth near the terminal claw. There are 3-4 denticles on each
side of the anus. This armature of the post-abdomen distinguishes the
species at once from Ilyocryptus sordidus and I. acutifrons, while the
~antennary set89 distinguish it from I. agilis. The fact that moulting is
imperfect also serves to distinguish it from the latter species.
  This is the common form of Ilyocryptus here, and is very abundant in
shallow water and marshy localities throughout the summer and until
after the formation of ice in the winter. The failure of food consequent
~on long continued cold seems the only thing which checks their multi-
plication. Whether I. spinifer, Herrick (op. cit., p. 77), is identical with
this species can not be decided as none of the specific characters are
mentioned or figured.
  The shell-markings in my specimens are far more distinct than those
described by European authors. Otherwise the species agrees -entirely
with the descriptions.
Species 40. ALONA LINEATA, Fischer.
  if, following Matile's *advice, the spiecific name lineata is abandoned,
-my form would be A. pulchra, Hellich.
Species 44. ALONA LEPIDA, sp. nov. Plate XIII. Fig. 19.
         Length, .8 mm.             Length of male,.6 mm.
         Height,.45-50 mm.          Height of male,.3 mm.
         Length post-abdomen,.40 mm.
  General shape conforms to the normal Alona type. Head depressed,
i stru sub-acnute.  arm ac       t   evel of the ventral margin of the
shell.c Valves quadrangular, dorsal margin arched, superior posteal
angle obtuse, well-marked. Posterior margin oblique, bearing a row of
minute spinules. Inferior posteal angle rounded, very slightly emargi-
nate. Ventral margin beset with a row of plumose sete, of ordinary
length, which ends abruptly at the posteal angle. Valves marked by
close-set, conspicuous, longitudinal strin, alternately stronger and
weaker, occasionally anastomosing, running parallel to the dorsal and
ventral margins and converging into a reticulated area at the anterior
inferior portion of the valves. Between the stri. lie the braces.
  Antennule extends nearly to end of rostrum: is spindle-shaped, largest
near base, provided with an anterior sense-bristle and 6-8 subequal
sense-hairs. Antennary seth or. The terminal set.e are of unequal
length. Al are plumose and without spines. The eighth setd p  is of
moderate size, bi-articulate and plumose. Spines of antennae,I. On the
middle joint of the inner branch is a circlet of small spines. Ventral
margin of labrum often notched just anterior to the posterior angle,
* Matile, P. Die Cladoceren der Umgegend von Moskau, 1890, p. 46.
. I

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