28 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxii. 



form of the adult male, corresponding perfectly with the same form of the European 

 species figured and described by Dr. Sars, I have not been able to find among the 

 numerous specimens from Lake Superior. A single specimen of this form of the 

 male was, however, sent to me by Dr. Stimpson under the manuscript name of 

 Gammarus Hoyi, while two specimens of the female were sent as Gamrnarui< brevistylis. 

 These are undoubtedly the same as the Gammarius Ilot/i and brerixtilKs mentioned, 

 without descrii)tion, by Dr. P. R. Hoy. « 



PONTOPOREIA FILICORNIS Smith. 



Gammarus fiUcornis Stimpson, MSS. 



Pontoporeiafilicornis Smith, Rep. IT. S. Fish Com., 1872-73 (1874), p. 649. 



Professor Smith's description follows: 



Male. — Outline of the head very much as in P. affinis. Eyes about as large as in 

 that species, slightly elongated, black. Peduncle of the antennula reaching nearly 

 to the distal end of the penultimate segment of the peduncle of the antenna, about 

 as long as the head and the first segment of the thorax together; first segment large 

 and thickened; second half as long as the first; third slightly more than half as long 

 as the second. Flagellum greatly elongated and very slender, reaching nearly to the 

 tip of the abdomen, and composed of thirty-three segments, of which the proximal are 

 longer than broad, while they increase in length distally, until, near the tip, they 

 are many times longer than broad, and exceedingly slender. The upper side of the 

 flagellum is nearly naked, only the alternate segments being furnished with two 

 minute seta' near the distal extremity, while the under side of each segment is armed 

 distally with minute setae, and most of the segments with one or several clavate 

 (olifactory) papilLe, and many of the segments have in addition a peculiar trans- 

 parent, shallow, bell-shaped appendage, raised on a very slender peduncle. Sec- 

 ondary flagellum reaching to the fourth segment of the primary, and composed of 

 four segments, of which the terminal one is very short. Penultimate segment of the 

 peduncle of the antenna about as long as the first segment of the peduncle of the 

 antennula; ultimate segment slightly shorter; penultimate and antepenultimate seg- 

 ments furnished with long, plumose hairs below and several fascicles of short, seti- 

 form hairs above. Flagellum much longer than the flagellum of the antennula, very 

 slender, and composed of about fifty very elongated and somewhat flattened seg- 

 ments, which have about the same proportions as in the flagellum of the antennula, 

 and are furnished with the same kinds of appendages. 



Epimera of almost exactly the same proportions and form as in P. ajfinis, and the 

 first four margined with plumose hairs in the same way. First pair of legs very 

 nearly like those of P. affinh; the palmary margin even slightly more longitudinal 

 than in that species, continuous with the posterior margin, and armed with two small 

 obtuse spines near the tip of the closed dactylus in addition to the setiform hairf. 

 Second pair of legs of the same form as in P. affinis, except that the palmary margin 

 is slightly concave and a little oblique in a proximal direction; the posterior mar- 

 gin furnished with fascicles of setiform hairs, as in that species, and armed close to 

 the palmary margin with three or four small obtuse spines. Third and fourth pairs 

 of legs like those of P. affinis, except that the dactyli have each three setiform hairs 

 near the tip, being in this as in several other respects nearer P. Ifoyi. Fifth and 

 sixth pairs of legs almost exactly as in P. affinis, except the posterior margin of the 

 propodus in the sixth pair is armed with three pairs of small spines. Seventh pair, 

 of legs having a few small spines on the propodus, but otherwise as in P. affinis. 



Lateral margins of the first second, and third segments of the abdomen with the 

 angles rounded; lateral margin of the third segment furnished with a line of several 

 submarginal, plumose setse near the anterior angle, and behind them armed with five 

 large and acute spines directed backward, of which four are in pairs near the middle of 



«Deep Water Fauna of Lake Michigan, Trans. Wis. Acad. Sci., 1870-72, p. 98-101. 



