PACKAED ON NEW PHYLLOPOD CRUSTACEA. 17o 



Male. — Carapace much flattened, oval-triangular, the dorsal edge 

 of the valve but slightly curved, the posterior end well rounded, while 

 the front end is but slightly curved. Head in front truncate, much as 

 in the females of L. gouldii and gracilicornis^ the end being broad and 

 square. Hand large, a little longer than broad, with the claw large, and 

 as long as the hand is broad. There are nine pairs of limbs, the ninth 

 ending in a pair of large, strong, recurved hooks. The end of the ter- 

 minal segment on its ventral side is rather more produced, and with a 

 more conspicuous spine than in the female. Two males occurred among 

 forty-four females. 



Length of carapace, d"^"" 5 breadth, 3.2"^^. 



Female. — Carapace scarcely distinguishable from that oiL. gracilicornis 

 in outline, though it varies slightly in form, some being quite round and 

 regular, others slightly ovate, and some quite flat and triangular. Mus- 

 cular impression as in L. gracilicornis, but the vascular impression is 

 much broader and proportionately shorter than in L. gracilicornis, 

 where the front of the head is suddenly truncate, and wider at the 

 extremity than behind in gouldii; while in gracilicornis it is also trun- 

 cate, but does not contract so much in front of the eyes, the narrowest 

 point being between the eyes and the end of the front. In the present 

 species, however, the front is very much produced into a long, acute, 

 mucronate point, with two teeth on each side, the middle tooth varying 

 much in length. The carina is very high and sharp. 



Antenuiie with the second joint half as long as the basal 5 four succeed- 

 ing joints very short, and together not as long as the succeeding seventh 

 joint, from which arise the flagellum, the upper branch of which is 

 15-jointed, the lower one 17-jointed, with ciliated hairs, the longest ones 

 as long as the entire antenna. Twelve pairs of feet. 



End of the body blunt, squarely docked, the point blunter than in L. 

 gouldii, and ending in a slender spine. Two dorsal terminal filaments, 

 much as in L. gouldii. 



Length of carapace, or shell, 4"^"" ; breadth, 3™°^. Foriiy-four females, 

 nearly all with eggs, occurred with Lepidurus couesii, in pools on the 

 west bank of Frenchman's Eiver, Montana, 49° N. It also occurred in 

 large numbers associated with Lymnetis hrevifrons in pools at Ellis, 

 Kans., collected by Dr. L. Watson June 29, 1874. The specimens were 

 females with eggs, and as a rule were triangular in outline, compressed, 

 only one or two of the Montana examples being so much compressed : 

 but the species is so easily recognized by the mucronate, tridentate front 

 of the female head, that I think no mistake has been made in the iden 

 tification of the Kansas specimens. 



Lymnetis goiddii Baird (Fig. 11, d). — I have received from Mr. S. A. Forbes 

 male specimens of this species from Normal, 111. The hand is much slen- 

 derer and the claw longer than in L. mucronatus, while the carina 

 on the front of the head is unusually high. In the female, the front of 

 the head is very sharply mucronate, with lateral angles, as in sharply 

 mucronate specimens of L. mucronatus. 



