W. Lilljeborg on the Genera Peltogaster and Liriope. 265 



analogy of Bopyrus abdominalis, Kroyer, may readily be ascribed 

 to difference of age, and perhaps of sex. The young animal 

 described by the author was only one-twelfth the size of that 

 described by Rathke. The latter is more elongated, and has 

 one more pair of thoracic feet; the first pair of antennae are 

 furnished with several setse; most of the thoracic feet are 

 apparently shorter; the abdominal feet are a little shorter; 

 and the caudal feet are differently constructed, being simple, 

 while the young observed by the author have them biramose. 

 But these and some other differences occur also between the 

 young male of Bopyrus abdominalis figured by Kroyer and the 

 still younger larvse of the same species. Hence the author 

 does not hesitate to consider the parasitic Isopod found by 

 him upon Peltogaster Paguri as belonging to the same species 

 as Liriope pygmaa. 



Now, as it lives parasitically upon Peltogaster Paguri, its pre- 

 sence in the cavity of the latter, where it was found by Rathke, 

 is explained without much difficulty. The Peltogaster may have 

 borne a fully developed female Liriope, which, after reproduc- 

 tion, had fallen off, whilst some of the young may have remained 

 behind upon the Peltogaster, and walked about until, finding 

 the orifice at the anterior extremity of the body, they en- 

 tered by it ; or they may have been in search of young females 

 upon the Peltogaster, and remained attached to the latter, just 

 as Kroyer found a male of Bopyrus attached to the eye of a 

 Hippolyte on which there was no female. The author is in 

 favour of the latter opinion, as he thinks that if a mature female 

 of Liriope had detached itself from the Peltogaster, the marks of 

 its adhesion could not have escaped Rathke's observation. 



With regard to the systematic position of Liriope, Rathke 

 was evidently w r rong in considering it as an Amphipod ; and in- 

 deed he indicates its " resemblance to some Isopoda of the genus 

 Idothea." Dana was the first to recognize its Isopod nature ; he 

 places it in the family Tanaidce. Steenstrup asserts it to be an 

 Isopod of the family Bopyridce ; and his view of the relationship 

 of Liriope, and its connexion with Peltogaster, is accurate. It is 

 with the Bopyridce that Prof. Lilljeborg arranges this singular 

 genus, of which he gives the following character : — 



Genus Liriope, H. Rathke. 



Animal e Crustaceorum classe, Isopodorum ordine, et Bopyridarum 

 familia. 



Fcemina adulta corpore in partes duas distinctas diviso ; anterior 

 sive cephalothorax, caput et tria segmenta sequentia comprehen- 

 dens, est cum posteriore indivisa parte majore, sive matrice, quasi 



Ann. Z$ Mag. N. Hist. Ser. 3. Vol.yi. 18 



