Crustacea from the Firth of Forth. 203 



subeqnal in length. Caudal stylets rather longer than the 

 last two abdominal segments and provided with four setas of 

 very unequal length, the inner one of the two middle setse 

 being much longer than the others and more than twice the 

 length of the stylet ; a small seta also springs from the outer 

 margin and near the middle of each stylet ; the stylets of the 

 male are rather longer than those of the female. Ovisacs 

 two, large. 



Huh. Within the siphons and between the branchial folds 

 and body of tlie common cockle {Gardium edule), Firth of 

 Forth and Morecambe Bay. 



Remarl-s. — This species, though differing somewhat from 

 the generic description of Lichomolgus, especially in having 

 the inner branch of tlie fourth pair of swimming-feet three- 

 jointed, agrees generally with the characters of that genus ; 

 it seems better therefore, for the present at least, to refer it to 

 Lichomolgus. 



Lichomolgus agih's was first observed in specimens of 

 Cardium edide from Morecambe, Lancashire, and more 

 recently in specimens of the same species of cockle from the 

 vicinity of Cramond, Firth of Forth. The Copepod was 

 obtained in at least 90 per cent, of the cockles examined, and 

 appears to be moderately common— as many as sixteen speci- 

 mens were taken from a single cockle. Tliey are very active 

 in their movements: if the shell of a living moUusk be 

 opened, so that some of the contained water remains in the 

 hollow of the opened shell-valves, the Entomostracan may be 

 observed darting hither and thither in the water ; not unfre- 

 quently their- presence is indicated only by the dark-coloured 

 Ime of the alimentary canal, their body being otherwise so 

 transparent as to be scarcely visible in the water. When the 

 Copepod is removed from the water, the ovisacs, when present, 

 are very conspicuous ; they are about half as long as the 

 animal, nearly straight along the inner edge, while the outer 

 margin is a flattened but evenly rounded curve. 



The presence of this Crustacean does not seem to be due to 

 or to indicate an unhealthy condition of the mollusk which 

 forms its host. 



'> Enterocola eruca, Norman. (PI. XVI. figs. 1-11.) 

 Enterocola eruca, Brady, Mon. Brit. Copep. vol. i. p. 147 (1878). 

 Description.— LQ.ngih, exclusive of ovisacs, 4-5 millim. 

 (nearly i of an inch), and including ovisacs 13 millim. (fully 

 \ an inch). Body seen from above somewhat cylindrical, 

 but rather narrower towards the anterior end, and composed 

 of four distinct and subequal segments ; there is a constriction 



