660 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



First pair of thoracic legs chelate; carpus small, triangular, and 

 closely united with the propodiis, which is thickened in the male, with a 

 broad, low tubercle on the inner margin a little above the base; dactylus 

 more than half as long as. the propodus, its palmary edge armed with 

 spines, of which the distal ones are the larger, and at the end with a 

 large spine ; carpus and propodus in the remaining six pairs of legs of 

 about equal length, movably articulated, and armed with acute spines 

 along their posterior edges ; dactylus much less than half as long as the 

 propodus, armed with spines along the posterior margin, and biunguicu- 

 late at tip. Three proximal segments similar in all the legs, the first 

 being longest, and the third short and triangular, or quadrant-shaped. 



The first abdominal segment is furnished, in the males, with two pairs 

 of appendages, of which the outer is composed of a small oval plate, 

 with a few articulated spines along the inner border, and articulated at 

 its extremity with a larger and longer plate, which is expanded along 

 its outer border, and ciliate along its exterior and distal margin. The 

 inner or upper pair of appendages consists, on each side, of a robust 

 quadrate plate, to the distal margin of which two biarticulate rami are 

 attached. The inner ramus has its proximal segment short, much 

 expanded, but not in the form of a hook, as in A. aqiiaticus as figured by 

 Sars;* its terminal segment is pear-shaped, as in that species. The 

 outer ramus has its proximal segment also expanded and triangular; 

 the distal segment quadrate and ciliate externally and distally. 

 The corresponding abdominal segment, in the females, with a single 

 pair of plates, which are subquadrant-shaped but broader than long, 

 with their inner margins straight and meeting each other on the 

 median line. Outer plates of the next pair of abdominal appendage^s 

 thickened, and forming an operculum covering the remaining branchial 

 plates. These opercular plates are semi-ovate, truncated at the extrem- 

 ity, straight on the inner side, and meet along the median line. They 

 are each divided into two very unequal portions by a suture, running 

 from near the end of the inner straight margin, diagonally across the 

 plate, to a point on the outer curved margin about one-third of the way 

 from the base to the apex; the distal portion is thus much the smaller. 



Posterior pleopoda, or caudal stylets, slender; proximal segment 

 somewhat larger than the fourth segment of the antennae, cylindrical, 

 SbS are the two rami, of which the outer is only half as long as the inner. 



Length, excluding antennte and caudal stylets, 8""" to 13™". 



•Color above dark-fuscous, spotted, and mottled with yellowish. 



Common among Cladophora, in 8 to 13 fathoms, on the south side of 

 the island of Saint Ignace, also in 4 to 6 fathoms at the eastern end of 

 that island, and in 6 to 8 fathoms among the Slate Islands in Lake 

 Superior; and since collected by Mr. J. W. Milner on algte drifted into 

 nets, 30 fathoms. Thunder Bay, Lake Huron. 



*Histoire Naturelle des Crustaci^s d'Eaii Douce de Norv^ge, 1« livniisou, pi. x, fig. 

 6, 1867. 



