on the Ephemeride. 93 
eequalis; secundus brevior: inferioris primus articulo- 
rum multo largissimus, ceteris conjunctim longitudine 
subzequalis ; tertius conicus, secundo semi-zequalis. 
Pedibus anticis depressis, alis duabus late expansis 
(fere nunquam erectis), et setis tribus subqualibus 
pubescentibus parallelis, subimago quiescit. 
Imago. Caput et prothorax transversi; oculi remoti, 
integri. Ale duz magne, in longitudinem marginium 
terminalium ciliate. Tarsi quinque-articulati (intermedi 
interdum tamen quadri-articulati): posticus proximo ar- 
ticulorum brevissimo, tibizque adnato, secundo tertio 
et quarto brevibus subzqualibus, quinto ceteris lon- 
giore: anticorum ungues breves, obtusi, conformes ; 
posteriorum ungues dissimiles. Sete tres subsequales, 
internodis (in ¢) longis. Forcipis pedes inarticulati. 
Ovivalvuli femina caret. Latera sezmentorum abdominis 
plus minusve retro producta. 
These insects live a very short time in their adult state. 
They fly in dense crowds over gentle streams, rivers and 
lakes, early in the morning and late in the day, at the 
beginning and end of summer. Dr. Hagen says that, in 
Prussia, the English species sometimes appear “in such 
quantities that objects near the water are covered an 
inch thick, and in the Curische Nehrung they are used 
to feed the pigs.” With us, they are less abundant. 
re 
Cenis macrura. 
(Genitalia maris, Pl. V. fig. 4.) 
Ephemera brevicauda, Fab. (§ sub. ?) 1798. C. ma- 
erura & interrupta, Ste. 1835-6. [H. pusilla, Zet. MS., 
1840.] OC. grisea, Pict. 1843-5. 
Subimago, v. v.s. Ale griseo vel nigricanti tincte, 
preecipue costas versus. Set nigricantes. 
Imago, v. v.s. Caput nigrum, articulis antennarum 
proximis duobus, et junctura capiti-thoracici, cervinis. 
Prothorax corvinus: meso- et meta-thoraces aterrimi 
nitentes. Pedes ¢ femoribus atris, tibiis tarsisque pal- 
lide nigricantibus: ¢ femoribus anticis griseis, posticis 
cretaceis. Abdomen 6 griseum, latera versus corvi- 
num; segmentorum intermedia singula supra lineis in 
mediis longitudinalibus, punctis duobus apud bases duo- 
