Bocquet, Hoestlandt & Levi
Body oval in outline, readily rolling into a ball. Antenna 1 with 9 to 15 aesthetascs. Maxillipede palp with prominent lobes fringed with smooth setae on articles 2 to 4.
Five anterior pleon segments all fused; sixth pleon segment fused with the telson as a pleotelson which articulates freely with the pleon. Coxal plates of pereion segments 2 to 7 fused with the segments. Pereiopod 1 with up to 70 smooth setae on the ischium and about 100 on the merus, and 3 to 8 in a distal row on the propodus. Pleotelson rounded or only slightly acute at the apex, without a mid-ventral respiratory channel and posterior border not notched. Pleotelson with a smooth dorsal surface; posterior border extending beyond uropod in large males. Uropods lateral, with the expod and endopod subequal in length, endopod rounded at the apex. Uropods usually with 4 to 7 slight serrations on the outer margin of exopod. No sexual dimorphism.
Males recognizable from 4.0 mm body length, ranging to 12.0 mm; females range from 4.0 to 8.0 mm.
A brackish species which occurs under stones and sometimes in rock crevices between MTL and LWN, replacing Sphaeroma serratum in the middle reaches of estuaries. Sometimes on marine shores where freshwater flows over the shore.
In the British Isles recorded from south and southeast England, Wales and eastern Ireland. On the European coasts it ranges from Belgium to northern Spain.