No. 26.] ARTHROSTRACA OF CONNECTICUT. 2IQ 



First antennae extending to end of second joint of second 

 antennae, with first and second joint not enlarged and subequal; 

 third and fourth joints subequal and each somewhat longer than 

 either of the preceding. Second antennae with first joint very 

 short; second and third joints subequal; fifth joint a little longer 

 than the fourth which in turn is longer than the third ; flagellum 

 composed of eight joints. 



Thoracic segments subequal ; first embracing the head slightly 

 on either side; lateral portions of the segments curved outward 

 and somewhat upward forming an angle with the portion of the 

 segment to which it is adjacent. Coxal plates from the second 

 to the seventh inclusive, extending entire length of each segment, 

 and very large and wide, increasing in width to the seventh, and 

 giving a serrated appearance to the sides of the thorax. 



Legs all more or less alike in character, robust, and with 

 free margins of all the joints and lower margin of the propodus 

 setose. 



Abdomen composed of two short segments and a long telson 

 with indications at the sides of coalescence of another short seg- 

 ment. Telson with sides nearly parallel beyond the middle and 

 broadly truncate or even slightly emarginate behind. Basal plate 

 of operculum elongated and with parallel sides; terminal plate 

 less than one-fourth as long and tapering slightly. 



Length of male 28 mm. ; of female 22 mm. 



Distribution: Patagonia; New South Wales; Borneo; be- 

 tween Montevideo and Straits of Magellan; southwestern Ire- 

 land; Mediterranean; Florida Keys; North Carolina; off Mary- 

 land; Chesapeake Bay; south shore of Long Island; Vineyard 

 Sound; Woods Hole, Massachusetts; Newport, Rhode Island; 

 off Marthas Vineyard; near Isles of Shoals; Halifax, Nova 

 Scotia. 



This species is pelagic, it is found swimming free as well as 

 among masses of floating seaweeds. 



It is easily distinguished from other species of the genus by 

 the telson which is broadly truncate and not the least pointed. 

 From other genera of the New England coast, Idothea is dis- 

 tinguished by the abdomen of apparently four segments of which 

 the first three are short and the third is united in the dorsal region 

 to the large vaulted telson; by the conspicuous two-valved oper- 



