40 CARL BOVALLIUS, AMPHIPODA HYPERIIDEA. I. 2. THAUMATOPSIDtE. 



which he would call Cystosomidce. In the above cited paper I proposed the name Thau- 

 matopsida? for the family, it being unfit to employ a family name which is not deri- 

 ved from a generic name in use within de family, and when Cysteosoma, Cystisoma or 

 Cystosoma was justly rejected as being preoccupied, I could not maintain the proposed 

 name Cystisomidce or rather Cystisomatidce, as it ought to have been written. Th. Stebbing, 

 however, regarded my reasons for rejecting the old name as not valid, and restored both 

 the names viz; Cystisoma and Cystisomidce, presuming that ethymological correctness is not 

 needed in writing zoological names, and that the difference between Cystisoma and CystO- 

 soma is sufficient to allow the keeping of both alive, although both really are the same name. 

 I cannot but oppose this opinion and still believe that each genus must have a name by 

 itself, orthographically written. Therefor I still retain the names Thaumatops and Thauma- 

 topsidse. 



The biological notices about the members of the family are very meagre. We only 

 know that the most of the very few hitherto recorded specimens, the seven captured du- 

 ring the Challenger Expedition, have been dredged from a depth varying from 500 to 

 2500 fathoms; the previously known specimens were taken floating on the surface of the 

 sea, as far as I could ascertain. 



The enormous size of the body seems to be in some way connected with the ani- 

 mal's power of floating and diving, as the most of the interior of the body is occupied 

 by a kind of vesicle filled with some fluid. It is very probable that the animal possesses 

 means to change its specific gravity by compressing or dilating the vesicular room thus 

 increasing or diminishing the amount of fluid in it, but I have not been able to detect 

 neither muscles on the walls of the vesicle, nor any outlet from it. 



As to their geographical distribution, they must be considered as chiefly tropical or 

 subtropical animals, they are, however, widely spread out over the surface of the seas and 

 probably more widely than most of the other Hyperids owing to their strongly developed 

 floating powers. 



Hitherto the family contains only one genus. 



Genus 1. THAUMATOPS, R. von WILLEMOES-SUHM, 1878. 



Diagll. Caput plus minnsve sphaaricum. Antennae secundi paris tubercula minima formant. Pedes 

 perm primi et secundi parium cheliformes. Ejrimera indistincta. Pedes uri crassi, ramis 

 internis cum pedunculis coalitis; pedes secundi paris desunt. 



The head is more or less spherical. The second pair of antenna' form very small tubercles. 

 The first and second pairs of perceopoda are cheliform. The epimirals are indistinct. The 

 nropoda are thick, prismatic; the inner rami are coalesced with the corresponding pedun- 

 cles; the second pair are wanting. 



