Rev. Canon A. M. Norman on British Mysidai. 153 



In the male the pleopoJs have the branches very long, 

 composed of twelve to fourteen articulations ; the inner 

 brancli furnished at the base with a lateral leaf-like process 

 (as in the genus Leptomysis) instead of the bilobate and con- 

 voluted organs usual in the genus Siriella. Length 25 

 millim. 



In consequence of the absence of convolution in the organ 

 attached to the pleopods of the male in this species Glaus has 

 constituted a genus for its reception under the name Pseudo- 

 siriella. 



Hah. Plymouth, 8 fath., August 5, 1889 (.4. M. N.). 

 ^^Mysis producta " was taken by Gosse at Weymouth. 



Distribution. Adriatic [Claus) : Mas. Nor. Nice {M.- 

 Edwards) ; Algiers {Lucas) ; Goletta, Cagliari, Malta, and 

 Syracuse {G. 0. Sars) ; Black Sea {Grehnitzky). 



Subfam. II. Gastbosaccin'jb. 



Genus 2. Gastrosaccus, Norman, 1869. 



=Acanthocaris, Sim, 1872, and Pontomysis, Czerniavsky, 1882. 



Carapace deeply emarginate dorsally behind and usually 

 cut into lobes at that part. First segment of pleon in female 

 provided with a very large epimeral process which acts in 

 support of the incubatory pouch ; that poucli is formed of 

 two pairs of plates. Eyes small, cylindrical. Peduncle of 

 antennules of great length and very strongly built, their outer 

 filament much swollen at the base. Antennal scale small, 

 shorter than peduncle, outer edge naked, terminating in a 

 spine-point. Legs having tarsus multiarticulate, bearing 

 spines as well as setaj at each articulation ; no nail ; first 

 2)leopods in female well developed, consisting of an elongated 

 curved cylindrical peduncle (which is wider at the extremities 

 than in the middle) and two minute one-jointed branches ; 

 remaining pleopods in female very small and simple. Tel- 

 son quadrangular, elongated, with a short cleft at the apex ; 

 this cleft margined with serrations, which are larger distally ; 

 sides of telson bearing spines of unusually large size. Outer 

 uropods oue-jointed, their outer edge beset with a series of 

 strong spines. 



In the male the sexual appendage of the last joint of 

 peduncle of antennules is small and merely nodulous. All 

 the pleopods are biramose and in a great measure formed for 

 swimming. Peduncle of first pair margined with long setse; 

 peduncles of remaining pairs naked ; inner branch of first, 



Ann. d- Mag. N. Hist. Ser. G. Vol. x. 1 1 



