64 BRITISH COPEPODA. 



devoid of spines. Inner tail seta twice as long as tlie 

 outer, and about equal in length to the abdomen. 

 The inner branches of the swimming-feet in the male 

 do not greatly differ from those of the female. Length 

 3^rd of an ioch ('77 mm.). 



The localities in which I have met with this species 

 are few, but in these it occurs pretty plentifully ; in a 

 brackish tidal pond at Westport (Mayo) ; in a pool 

 just above high-water mark, and in ditches amongst 

 Utricularia minor, near Clifden (Galway) ; also in 

 brackish pools at Pensarn, Merionethshire. 



2. MESOCHEA ROBERTSONI, nov. sp. PL XLVJI, figs. 



115. 



Animal robust; abdomen not much more slender 

 than the thorax, in the female 4-jointed, the last joint 

 short, and forming a projecting process at the posterior 

 dorsal angle ; caudal segments scarcely as long as 

 broad; anal operculum strongly denticulated (fig. 15). 

 Anterior antenna much shorter than the first body-seg- 

 ment, slender, 8-jointed (fig. 2), the joints nearly equal 

 in length ; accessory branch of the posterior antenna 

 small, 2- jointed. Posterior foot- jaw (fig. 6) small and 

 slender. First pair of feet (figs. 7, 8) very small, 

 larger in the male ; inner branch composed of two 

 nearly equal joints, and only slightly longer than the 

 outer branch ; inner branches of the second, third, 

 and fourth pairs (figs. 9, 10, 11) short, the first joint 

 extremely small. Basal joint of the fifth pair very 



