Thomson. -^0/i a Xew Parusilic CojjejJod. 221 



Art. XXVII. — A Neic Paraiiitic Copejiod. 

 By George M. Thomson, F.L.S. 



[Read before the Otarjo Institute, Uth October, ISOO.] 

 Plate XXIII. 



As far back as May, 1889, Mr. J. F. Erecsou sent me a tube 

 containing numerous specimens of a small pai'asite taken from 

 the bodies of Mokis [Latris ciliaris). In my paper on jjara- 

 sitic Copcpoda, react last year," I inadvertently omitted to in- 

 clude this very distinct "form. It belongs to the genus Lepc- 

 ophtheims, and I have much pleasure in naming it after its 

 discoverer, to whom I am indebted for many valuable observa- 

 tions on our fish-fauna, and for numerous specimens illus- 

 trative of their food-sujiply, their parasites, etc. The following 

 is a description of the species : — 



Lepeophtheirus erecsoni. Plate XXIII., figs. 1-11. 



-l/«/c! (fig. 2) . — Body very fiat. Cephalothorax semi-orbicular ; 

 hind-margin nearly square, outer margin rounded posteriorly, 

 and finely fringed with extremely numerous delicate seta). This 

 fringe is more like a border of transparent tissue than a flange of 

 setae. Frontal lobe extending across only a small portion of 

 the front of the cephalothorax (about one-fourth of its breadth), 

 slightly notched in the middle, separated at the sides from the 

 cephalothorax only by a slight indentation. Plind portion of 

 thorax barely half as long as cephalothorax, and not more 

 thaii one-fourth as wide. Fourth segment quite destitute of 

 dorsal lamella?, very short and broad. (Jcnital segment rather 

 longer than broad, its lateral margins shorter than on the 

 median line, ending in somewhat rounded lobes tipped with 

 3 or 4 seta? ; hind-margin nearly square. Abdomen extremely 

 short, indistiiictly 2-iointed. Caudal lamella? very short, 

 terminathig in a few (8 or 4) short settc. 



Length of whole animal, barely 3mm. ; breadth of cai'apace, 

 about 2nnn. 



Female (fig. 1). — Cephaloth(M-ax orbicular, rounded Ijchind ; 

 outer margin as in the male. Frontal lobe rather more 

 arcuate than in male. Hind portion of thorax half as long as 

 cephalothorax, and nearly half as wide. Fourth segment very 

 short. Genital segment much longer, subquadrate, produced 

 backwards on each side into rounded lobes. Abdomen very 



* Trans. N.Z. Inst., vol. xxii., p. 353. 



