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 pygmcea, the relation between that animal and the Pelto- 

 gaster Paguri is easily understood. Liriope is therefore an Isopod 

 which lives parasitically upon Peltogaster y 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 [cephalothorax) 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 antennae. Beneath, 

 between the first and second segments, is a brown transverse 



* This part is deeply tixed in the integument of the Peltogaster, even 

 perforating its inner lining membrane. 



