CRUSTACEA. 



PODOPHTHALMIA . 



Mysis relicta Love"n. — About ten years ago the Danish naturalist Loven* described a 

 species of Mysis under this name from Lakes Winer and Wetter, in Sweden. It was 

 found in company with Pontoporeia affinis Lindstrom, Pallasia eaneelloides (Gerstfeldt 

 sp.), Gammaracanthus loricatus Bate and Idotwa entomon, the last two being known also as 

 marine species. Love"n describes the species of Mysis as closely allied to the M. occulata 

 Fabricins, a marine species found on both sides of the Atlantic, and he regards its occur- 

 rence, and that of the Pontoporeia, as evidence that the lakes where it is found were for- 

 merly filled with salt water, that they had been cut off from the sea by the elevation of 

 the Scandinavian peninsula, and that the differences between these species of the lakes 

 and their allies of the neighboring oceaii have been brought about by the gradual changes 

 in the habitats of the lake species. I have compared specimens of the Mysis and Pon- 

 toporeia from Lake Wetter with those from Lake Superior, and I am unable to find any 

 characters by which to distinguish the European from the American forms. G. O. Sara, 

 in his great work on the fresh-water Crustacea of Norway, describes this same species of 

 Mysis from LakeMjosen, where he found it in from 3 and 6 to 200 fathoms.t Sars, how- 

 ever, regards it as only a variety of the marine Mysis occulata. 



In Lake Superior, the Mysis, was found in a large number of the dredgings. It was 

 brought up with sand and mud from 12 to 14 fathoms among the Slate Islands, from 

 4 to 6 fathoms in the cove at the eastern end of St. Ignace, from 8 and 13 fathoms with 

 Cladophora, &c, on the south side of St. Ignace, and from deep water, in a large pro- 

 portion of the hauls, from 73 to 148 fathoms. 



Amphipoda. 



Pontoporeia affinis Lindstrom. — What has been said in regard to the identity of the 

 Mysis from Lake Superior and the Scandinavian lakes applies equalty well to this 

 species. I can find no good differences between the Lake Wetter and the American 

 specimens. Loven, in the paper referred to, regards the European form as closely allied 

 to the Pontoporeia femorata Kroyer from the Greenland seas; While Sars, who found it 

 in the small lakes near Christiania, has regarded it as a vai'iety of that species. In Lake 

 Superior it was abundant, and occurred at every dredging, from the shallowest to .the 

 deepest. 



Since the above notices of the species of Mysis and Pontoporeia were written I have 

 received through the coun.esy of Dr. Stimpson, of the Chicago Academy of Sciences, 

 the Mysis, three species of Amphipoda, and the Pisiditim dredged by him in Lake Michi- 

 gan in the summer of 1870, and of which a short notice was published by Dr. Stimpson 

 in the American Naturalist for September of that year. On comparison I find the Mysis 

 and one of the species of Amphipoda from Lake Michigan of the same species as the Mysis 

 and Pontoporeia from Lake Superior, while the other species of Amphipoda are quite 

 different from the Gammarus and Cranyonyx described beyond. Dr. Stimpson, however, 

 regards the forms from Lake Michigan as new species, but I am not aware that he has 

 compared them with specimens from the European lakes. 



Cranyonyx gracilis Smith, sp. nov. — Eyes slightly elongated, black, composed of few 

 facets. Antennuloe slender, slightly more than half as long as the body; secondary 

 flagellum but little longer than the basal segment of the primary. Antennae much 

 shorter than the antennulae ; the flagellum and peduncle of about equal length, the 

 peduncle being a little longer than the peduncle of the antennuhB. Gnathipoda sub- 

 equal in both sexes, the second pair being only slightly lai-ger than the first; propodus 

 in the first pair quadrate, the palmary margin transverse, nearly straight, and armed 

 with slender spines, of which one or two at the prominent posterior angle are much 

 larger than the others ; propodus in the second pair like those of the first, but a little 

 more elongated, and the palmary margin slightly oblique. Third, fourth, and fifth 

 pairs of pereiopoda equal in length, and the margins of their basa spiuulose. Ultimate 

 pleopoda reaching to the tips of the penultimate ; the outer ramus nearly twice as long- 

 as the peduncle, and armed with slender spines ; the inner ramus very minute, shorter 

 than the width of the outer. Telson scarcely as long as the bases of the ultimate 

 pleopoda, slightly broader than long, and the posterior margin with a triangular emar- 

 gination, either side of which the extremity is truncate and armed with several spines. 



The incubatory lamellae of the female are very large, projecting much beyond the 

 coxae of the anterior legs, as in C. recurvatus Grube, (Archiv fur Naturgeschichte, xxxii, 

 p. 410, pi. 10, fig. 1,) which our species much resembles in the form of the autennulai, 

 antennae, gnathepoda, &c, while it differs much in the ultimate pleopoda and in the 

 form of the telson. Length 6 to 7 mm . 



* Om nagra i Vettern och Venern fauua Crustacoer Oversight at' Kongl. Vetenskaps-/-Akademiens 

 Forhandlingar. Stockholm, xviii, 1861, p. 285. / . 



t Zoological Record for 1867, p. 617. W 



