58 BRITISH PARASITIC COPEPODA. 



Antennules moderately stout ; sternal fork rather 

 small, narrow, and elongated, rami not divergent or 

 but very slightly so. Fourth pair of thoracic legs 

 stout, comparatively short, basal joint about as long as 

 the ramus, which is composed of three short and 

 moderately stout joints, the first being the largest, 

 and having the outer distal angle produced so as to 

 reach to near the end of the second joint, the first and 

 second joints each provided with a moderately stout 

 spiniform seta on the outer distal angle, the third joint 

 of a triangular form and carrying three spiniform 

 setae, the end one being rather stouter than the others ; 

 the apex of the joint is produced slightly beyond 

 the base of the end spine, forming a blunt-pointed 

 knob fringed with minute setae. From the peculiar 

 form of the first and third joints the marginal and 

 terminal setae are crowded together, and as each seta 

 is slightly longer than the preceding one, they impart 

 a character to this species somewhat different from 

 others, such as Calif/nx i-p<ix. Fifth pair very minute. 

 Egg-strings tolerably elongated. 



This species appears to vary in length : the speci- 

 men figured here measured about 5*5 mm., and 

 C. B. Wilson gives the length of his specimens as 

 3*3 mm. 



Male. The male of this Cali(jn** does not appear to 

 have been previously met with, and we are inclined to 

 consider that it is much rarer than the female. The 

 specimen of the male figured on PI. LXXI, fig. 14, is 

 the first and only one we have yet secured. It repre- 

 sents the result of the examination of nearly fifteen 

 hundred mackerel. The specimen figured was found 

 on the inside of the operculum of a mackerel caught 

 in the northern part of the Irish Sea in July 1912. 

 On that particular occasion two hundred fish were 

 examined, and although several females \ver<> found 

 only a single male could be detected. r,///V///x 

 pelamydis resembles the male of Caligus rd/Hiv in 

 general appearance, and without careful examination 



