CRYPTOTHIRIA PYGM^EA. 263 



name had been employed four years previously for a 

 genus of Medusce, 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 Cirripedes, Steenstrup (subsequently, op. cit. 

 p. 214) abandoned his former opinion, leaving the ques- 

 tion unsettled. 



In the " United States Exploring Expedition," Crust, 

 p. 801, pi. 53 (1852), Dana described a new genus (which 

 he unnaturally placed in the family Tanaida>), 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 Balanidce. Three or four specimens 

 of the Crypto thir 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 



