Crustacea. 



6275 



name of genus). Filament two-jointed; basal joint minute, rounded, 

 nearly concealed by fifth joint of peduncle ; terminal joint rounded 

 and scabrous (Brandt failed to perceive the basal joint, and hence mis- 

 described the antennae as six-jointed). Abdominal rings, — coxae of 

 first and second obsolete. Telson (terminal ring), — coxa obsolete, 

 triangular. Posterior pleopods articulated to inferior margin of telson. 

 Peduncle completely exposed. Accessory lobe well marked. Acces- 

 sory appendage rounded. Ischium flattened, trigonal. 



Species Platyarthrus Hoffmanseggii, Brandt. 



Cephalothorax and abdomen covered with numerous rounded 

 granules, the margins of the wings distinctly crenulated through them. 

 Frontal lobe of head arched, fringed with coarse hairs, extending over 

 the entire front. External antennae densely scabrous and tuber- 

 culated. Eyes small, situated at external angle of head. Telson 

 triangular, with a shallow pit above its margins, slightly excavate ; 

 posterior margin fringed with hairs and tubercles. Last pair of 

 appendages,— peduncle subrotund, sides parallel, its superior margin 

 distinctly crenulated, scabrous. Accessory lobe arising from inferior 

 margin of peduncle. Accessory appendage curved and rounded, 

 barely attaining to apex of peduncle. Ischium scabrous, terminating 

 in a filament, equalling the peduncle in length. 



The specimens sent were all whitish gray. Mr. Hogan states that 

 the species is very active, does not roll, but merely feigns death when 

 alarmed, and conceals itself very rapidly. 



Crangon Pattersonii. 



During some dredging researches in Belfast Lough, last August, an 

 undescribed species of shrimp occurred to me, which I wish to record 

 under the above name. 



Rostrum nearly as long as the eyes, rounded at end, concave above. 

 Carapace with three rows of spines, viz., one median of three spines, 

 and one on each branchial region which bifurcates as it passes upwards. 

 Abdominal rings, — first to fourth smooth ; posterior margin of fifth 

 ring produced medianly into a triangular knob ; sixth ring flattened 

 above ; telson (last ring) lanceolate, sulcated above ; the fourth to 

 sixth rings narrow suddenly, as in C. fasciatus. 



The species is closely allied to C. spinosus, which differs in having 

 a narrow rostrum acute at end, and the rings of the abdomen from the 

 first to the fifth carinated. These distinctions hold good even in small 

 specimens. The specimens obtained were male and female, the latter 



