W. Lilljeborg on the Genera Peltogaster and Liriope. 261 
the town of Molde in Norway, at a depth of from 5 to 6 metres, 
amongst other Paguri, a rather small specimen of P. pubescens, 
which had a Peltogaster on its abdomen. This Peltogaster 
(Pl. IV. fig. 1) appeared to be double, or composed of two. As 
only one of these (a), which was of a reddish colour, contained 
ova and young, the author supposed at first that it was a bag 
of eggs attached to the body. But, as there was only a single 
bag of eggs, it departed from the Suctoria, in which there are 
usually two, although at the first glance Peltogaster appeared to 
approach that group in its structure. The doubt thus raised, as to 
whether the relation between the two parts was that of a maternal 
animal and an egg-sac, was confirmed by the supposed egg-sac 
exhibiting strong contractions, although no similar movements 
were observed in the supposed body of the Peltogaster. These 
contractions continued until the fourth day, and even after the 
Peltogaster had been dissected and the abdomen of the Pagurus 
had become putrid. On examining the young contained in the 
supposed matrix (fig. 4), Prof. Lilljeborg found that they were 
quite different from those of Peltogaster ; and a further exami- 
nation of the sac showed it to be a distinct animal, parasitic on 
the Peltogaster. The structure of the young proved them to be: 
Isopoda; and as it accorded perfectly with that of Rathke’s 
Liriope pygmaa, the relation between that animal and the Pelto- 
gaster Paguri is easily understood. Liriope is therefore an Isopod 
which lives parasitically upon Peltogaster, and probably also upon 
other Crustacea. Cavolini’s observations prove that this, or a 
nearly allied form, is sometimes found attached within the body 
of certain Brachyurous Crustacea; and Dana has several times 
found in a Balanide a parasitic Crustacean (the Cryptothir) be- 
longing to the same family as Liriope. These two animals may 
probably belong to a single genus. 
The following is an abstract of Prof. Lilljeborg’s detailed 
Latin description of the mature female filled with ova and newly- 
hatched young (PI. IV. figs. 2 & 3) :— 
Length from the mouth (2 a) to the opposite part of the body, 
where the anus appears to be, 4 millim.; breadth (from c to d) 
7 mill.; thickness 3 mill. The body is composed of two distinct 
parts. The anterior part (cephalothoraz) forms the organ of 
adhesion *; it is convex and smooth above, concave beneath, 
and exhibits above four distinct segments, of which the two 
middle ones are larger than the others. These segments are 
sinuated in the middle in front, and deflected and reflected towards 
the sides. There is no indication of eyes or antenne. Beneath, 
between the first and second segments, is a brown transverse 
* This part is deeply fixed in the integument of the Peltogaster, even 
perforating its inner lining membrane. 
