Harris: The copepod genus Porcellidium 
105 
as an adult female) Brady (1880). (C) Porcellidium viride male antennules (showing very long first seta on segment 2), Brady (1880). 
(D) Porcelloides tenuicaudus (Claus, 1860). Adult female with eggs and four spermatophores attached (freehand sketch of specimen in 
the NHM collection, V. A. Harris). (E) Female lifting body with PI limbs to irrigate eggs. 
complicated by wrong identification of animals. Claus (1889) 
acknowledges that his P. dentatum is really the male of P. 
tenuicauda , but his (1860) drawing of male P. dentatum is of 
a male P. fimbriatum. Similarly, Brady’s 1880 drawing of P. 
fimbriatum is clearly the adult female of P. viride. 
From this confusion and the absence of accurate 
description it is not surprising that later authors disagree on 
the true identity of P. viride and the diagnostic characters of 
the genus Porcellidium. 
The confusion between “ viride ”, “ fimbriatum ”, 
“ lecanoides ” and “ sarsi ” 
Brady thought that the large females in his collection were 
a different species to his P. viride and identified them as 
P. fimbriatum Claus, 1863, but Claus’ description is not 
very clear and his illustrations do not show a single species 
specific character that would have enabled Brady to identify 
his animals correctly. The most obvious difference between 
the two species is the placement of the (3 caudal seta, but this 
is not shown by either Brady or Claus. A revised description 
of P. fimbriatum was given by Claus (1889) in which at least 
eight specific characters are mentioned or illustrated. This 
showed clearly that Brady’s female was the adult female of 
P. viride and not P. fimbriatum. Paradoxically, Claus makes 
the mistake of stating that both Brady’s P. fimbriatum and P. 
viride are synonymous with his P. fimbriatum 1863. 
In the present study, samples collected from Laminaria 
digitata at Clachan, Seil Sound Oban, Scotland were found to 
have two distinct species living on the same seaweed, [Brady 
(1880) collected some of his specimens of P. viride at Loch 
Fyne, near Oban, Scotland], They are easily distinguished 
by their colouration and size. Adult males of the larger 
species have an unusually long first seta on segment 2 of 
the antennule (it is about 2Vz times the length of seta 2 and 
3, Fig. 7G). This is a unique species specific character that 
has not been found on any other known member of the 
Porcellidiidae. Brady’s illustration of the antennules of his 
adult male P. viride shows the same long first seta (Fig. 25C), 
therefore, the larger male animals from Scotland must be P. 
viride. The corresponding larger females clearly resemble 
Brady’s illustration of P. fimbriatum which must be the adult 
female of P. viride. It is of interest to note that animals from 
Norway identified by Sars (1904) as P. fimbriatum (and 
