CRYPTOTHIRIA PYGMA. 263 
name had been. employed four years previously for a 
genus of Meduse, by Lesson. 
Steenstrup, in the “Oversigt” of the Royal Danish 
Society for 1854 (pp. 145—148), considered that this 
minute Liriope, instead of having been devoured by the 
Peltogaster, was either a parasite upon it, or that it was 
its young state. Professor Schmidt having, however, 
shown that the young of the Peltogaster resembled that 
of the Cuirripedes, Steenstrup (subsequently, op. cit. 
p- 214) abandoned his former opinion, leaving the ques- 
tion unsettled. 
In the ‘‘ United States Exploring Expedition,” Crust. 
p- 801, pl. 53 (1852), Dana described a new genus (which 
he unnaturally placed in the family Yanaide), under the 
name of Cryptothir, remarking, as Steenstrup had done, 
that Rathke’s Liriope was not an Amphipod, but in reality 
an Isopod crustacean. Steenstrup had, however, referred 
Liriope to the family Balanide. Three or four specimens 
of the Cryptothir minutum were taken separately in as 
many individuals of the corallidomous barnacle, Creusia. 
In 1858 Lilljeborg found in the Norwegian Sea a 
Pagurus pubescens with a Peltogaster attached to its tail; 
but the parasite appeared to be double, one portion being 
filled with eggs, and which he consequently considered to 
be the single ovigerous sac of the parasite hanging sus- 
pended from the body, as is the case with the double egg- 
sac of the Cyclops, &c. But the fact that the Peltogaster 
was a suctorial animal, and not a mandibilated one (like 
the Cyclops), and that the egg-sac had motions inde- 
pendent of the Peltogaster, even after the latter had died, 
and the body of the Pagurus had putrefied, greatly per- 
plexed Lilljeborg. He then examined the sac and its con- 
tents more carefully, and discovered that the former was a 
distinct animal, parasitic upon the parasite, and that the 
