NO. 1507. FRESH- WA TER A MPHIPODA — WECKEL. 2 7 



extending nearlj' the whole length of the [)alinaiy margin. The dactylus is appar- 

 ently a little longer and more slender in the European specie.s. The ohliquity of the 

 palmary margin, and its armature near the posterior angle, seem to be always char- 

 acteristic of the American species. In the young specimens, however, there is often 

 but one spine, while in larger ones there are often three. In the third and fourth 

 pairs of legs of the American species the dact3'lus is usually armed on the inside, a 

 little way from the tip, with two setiform haii'S, while in the European species there 

 is only one. Some young specimens of the American species, however, agree with 

 the European in having but one hair upou the dactylus, while large ones often have 

 three, and in the full-grown male from Lake Michigan, mentione<l farther on, there 

 are even "four. 



The most remarkable differences are in thepeculiai', elongated, j)apilliform append- 

 ages upon the sternal portion of the thoracic segments. In the European species, 

 Dr. G. 0. Sars describes and figures an elongated and slender process depending 

 from the middle of the sternum of several of the thoracic segments; and in the single 

 specimen which I have examined, there are three of these processes, one each on the 

 second, third, and fourth segments. Dr. Sars, who has studied the living animals 

 very carefully, does not suggest what may be the use of the ajipendages, or whether 

 they ever vary in number or position in different specimens. In specimens from 

 Lake Superior there are usually seven of these appendages, one upon the second and 



N'Toi'OREiA HoYi. ( Aftrr Smith. ) 



two each upon the third, fi)urtli, and fifth segments. In form and size, these append- 

 ages do not differ, except that in alcoholic specimens they seem to l)e a little longer 

 in the American species. In some specimens of the American species, the append- 

 age upon the second segment is wholly wanting, and in two specimens examined 

 carefully there was only a single median one u{)on the third segment. In the 

 absence of all knowledge of the nature and use of these appendages, it seems useless 

 to speculate on their importance as distinctive characters. In a species of Ponto- 

 poreia from the Gn\i of St. Lawrence, which I suppose to be the P. affinis of Kroyer, 

 there are no such appendages on any of the thoracic segments. This fact, together 

 with the variation noticed in the specimens from Lake Superior, would seem to indi- 

 cate that these appendages are not of so much importance as might at first be 

 supposed. 



This species was found in great abundance in the dredgings in Lake Superior in 

 1871, and occurred in every haul from 4 to 169 fathoms. It was also dredged by 

 Mr. J. W. Milner in Lake Superior in 1872, in 60 fathoms off Outer Island. It is 

 common in the stomach of the whitetish from Lakes Superior and Michigan, and 

 probably also from the lower lakes. All the si^ecimens dredged in Lake Superior 

 were taken in August and the early part of September, and none of the females were 

 carrying eggs during that time. Females carrying eggs were dredged by Dr. Stimp- 

 son, in Lake Michigan, in 40 to 60 fathoms, off Racine, Wis., June 24, 1870, and 

 with them the adult male form with long antennulfe and antennte. This peculiar 



