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)
List of Crustacea Cladocera from Madison, Wis. 385 ber about eight and are placed on the posterior side of the distal end of the base. The flagellum is attached to the base with a distinct suture. Sars calls it "distinctly articulated" in L. australis. Whether he means that there is a movable joint he does not make clear. In L. occidentalis there is simply a distinct suture. The flagellum is long, curved back-- ward, tapers to a fine point, and is fringed with long straggling sense- hairs. These are far less numerous than in Latona. Most of them are on the anterior side of the antennale but at the tip they are attached top all sides. In this arrangement of the hairs the structure differs from the antennule of L. australis as figured by Sars. The sense-hairs are also longer than he shows them and the whole antennule is about twice as long, relatively, as that of L. australis. The antenna closely resembles that of L. australis. The basal joint is exceedingly stout, so that the branches look too small for it. The dorsal sames is bi-, the ventral tri-articulate. The setae are 0 ( - a.~~~~~~~~~~~~~~~~ - I,. and the spines 0-1-0 The basal joint bears the usual dorsal sense, organ at the base, and at-he distal end are a spine anteriorly and 'a Itplumose sense-hair behind. The proximal joint of the dorsal ramus, bears four well developed setme, and sometimes a fifth, proximal, seta which is much smaller than the others. Its presence or absence seems to depend on no law, asit is either present or absent in specimens of all ages and both sexes and may be present on one side and absent on the other side of the same individual. All setm are two jointed and densely plumose. The proportionate length of individual setas differs in my specimens fro atrali as g b The terminal sh I- iL, Of- --- ramus are little longer than the others in L. occidentalis. The seta of the second joint of the ventral ramus is as long as the largest on the distal joint and each is quite twice as long as any other seta on the branch. The post-abdomen closely resembles that of L. australis. It is short, fleshy, obtusely conical, and armed with nine very small super-anal den- ticles. The abdominal setm are two-jointed, plumose, each set on a fleshy projection. They are a little longer than those of L. australis. The terminal claws are strongly curved, and have two secondary teeth, of which the distal is the longer. The mouth parts and legs seem to resemble closely those of the other Sididce. No careful study of the legs, has, however, been made. They number six pairs, as in other Sididce. INTERNAL ORGANS. In the structure of the internal organs L. occidentalis agrees closely with L. australis, and I can add little to Sars' account. The general ar- rangement of the organs of the head may been seen in the figures. 25-A. & L. I 11, . j I I P I i
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