8 BRITISH COPEPODA. 
short and exquisitely plumed antenne, and (in the 
male) by the conspicuous posterior abdominal spine. 
It is certainly one of the most common, as it is also 
amongst the most beautiful, of British Copepods. The 
following are some of the localities in which I have 
taken it :—Abundantly on a sandy bottom off Seaton 
Carew (Durham), four fathoms; off Marsden, Sunder- 
land, and Seaham, twenty to thirty fathoms; Clifden 
Bay, Ireland, four fathoms; in tide-pools, Aranmore 
(Ireland) ; Lough Swilly, two fathoms; off St. Mary 
and St. Agnes, Scilly Islands, twenty to forty fathoms ; 
Shetland (Rev. A. M. Norman); on weeds at Bell. 
Rock Lighthouse (Mr. H. C. Davison). 
Genus 2. Horinosoma, Boeck (1864). 
Body much elongated, slender; abdomen not 
separated from the thorax by any distinct constric- 
tion, and remaining unflexed on the body after death 
(Pl. XXXVI, fig. 1). Head small, and united with 
the first thoracic segment. Anterior antenne (fig. 2) 
very short, much attenuated towards the apex, 5—7- 
jointed, bearing numerous long sete. Posterior an- 
tenne much larger and stronger (fig. 3), 3-jointed, 
and having attached to the first joint a long 2- or 3- 
jointed secondary branch; the last joint bears several 
strong, spine-like, plumose hairs. Mandible (fig. 4) 
slender, deeply cleft at the apex; palp large, 2-jointed, 
bearing several long sete and a short, simple, secon- 
