268 REPORT 1868. 



second, third, fifth, or seventh) with smaller spines, the rounded entire 

 apex terminating in four spines, the outer pair much longer than the 

 middle pair ; on examining the telson from below, it is seen to form, 

 for about half its length, an open tube, the opening consisting of a 

 central slit, the margins of which are edged with small spines. Interior 

 lamellae swollen at the base for the reception of the acoustic organ, but 

 afterwards very narrow, slightly longer than telson. Outer lamellae 

 remarkably long and very narrow, fully half as long again as inner 

 pair ; both margins of both pairs fringed throughout with long plumose 

 setae ; inner margin of inner lamellae also closely beset with spines, 

 which are of unequal size. 



In the male, the superior antennae have the last joint of the pedun- 

 cle furnished with the usual lobe and dense tuft of hair. All the pleo- 

 pods have a stout, large basal joint, which gives support to two branches, 

 the inner of which in the last four pair is multiarticulate and setose, 

 and gives off, close to the base, a small lateral lobe terminating in short 

 setae, but in the first pair the inner branch is rudimentary. The outer 

 branch in the first three and the last pair is also multiarticulate and 

 setose, but in the fourth pair is a more complicated organ, and consists 

 of six joints at the base, all furnished on each side with a long plumose 

 seta, and two branches of equal length, one slender, one-jointed, of 

 equal thickness throughout, ciliate, the other having a much stouter 

 basal joint and two multiarticulate ciliated filaments. 



A single male in 40-50 fathoms, 5-7 miles off Balta, in 1857 ; and 

 both sexes previously sent to me by Mr. Edward from Banff. 



The descriptions of Mysis gracilis and M. linguura, G. 0. Sars, come 

 very near to the female of this species, but the present is at once dis- 

 tinguished by having the antennal scale two- and not three-jointed. 



Genus GASTROSACCTJS, Norman. 



A genus of Mysidea. Female : marsupial pouch attached to last segment of 

 pereion and first of pleon. First pleopod composed of a much elongated basal 

 joint, and two short one-jointed branches ; second to fifth pairs consisting 

 of a single joint. Male having all the pleopods consisting of a basal joint, 

 and two branches differently developed on the different segments, and the 

 third pleopod the greatly developed sexual organ. 



Gastrosaccus sanctus (Van Ben.)= Mysis sancta, Van Beneden, Recherch. sur 

 la Faune Litt. de Belgique, Crustaces (1861), p. 17, pi. vii. figs. 1-4 

 (the male), = Mysis spinifera, Goes, Crust. Decap: Podophth. marina 

 Sueciae (1863), p. 14 (the female), = Gastrosaccus sanctus } Norman, Rep. 

 Brit. Assoc. 1867 (1868), p. 438. 



Female. Sides of carapace extending much beyond the dorsal portion, 

 which has its margin elegantly scalloped ; fifth segment of pleon pro- 

 ducing backwards on the back into a well-developed spine. Rostrum 

 slightly produced, rounded at the extremity. Eyes cylindrical, on short 

 peduncles. Superior antennae with greatly developed peduncles; first 

 joint as long as two following, cylindrical, smooth ; second joint half 

 length of last, with three large spines in a longitudinal row on the 

 outer margin ; filaments long and slender, the outer with its first joint 

 long (equal about eleven of inner), and furnished on its inner face with 

 a cutaceous process, apically setose, which reminds us of the lobe of the 

 males of Mysis. Inferior antennae having peduncle reaching the last 

 joint of peduncle of superior antennae ; scale short, subequal in length 



