8 C. BOVALLIUS. REMAREKES ON THE GENUS CYSTEOSOMA. 
The typical specimen, described by GuÉRIN, was taken by Mr 
PETIT DE LA SaUussAIE. The Challenger-specimens (if they are 
identical with that described above) were all captured in the 
south Alantic; all males. 
2. 'Thaumatops pellucida. R. v. WILLEMOES-SUHM. 
Syn. 1874. Thaumops pellucida. R. VON WILLEMOÉS-SUHM. Phil. Trans. 
Roy. Soc. 
” vol. 163, p. 
LA 4 629 
(non p. 638), 
pl. 49—50, 
fig. 1—9 a. 
Diagn. Caput segmentis quinque primis pereii longius, longitudine alti- 
titudinem superans. 
Segmentum primum et secundum pereii coalita. 
Antenne primi paris capite longiores, angulatae. 
Metacarpi pedum pereii parium duorum priorum processu carpi 
longiores. Pedes pereii quinti paris duplo p&ene longiores 
illis septimi paris. 
Segmentum ultimum wri carinatum. 
Pedunculi pedum wuri ultimi paris duplo longiores ramo externo. 
Ramus externus interno multo longior. 
The head is longer than the five first pereional segments, 
longer than deep. S 
The first and second pereional seoments are coalesced. 
The first pair of antenne are longer than the head, angu- 
lated. 
The metacarpi of the two first pairs of pereiopoda are longer 
than the corresponding carpal processes. The fifth pair of 
pereiopoda are a little shorter than twice the seventh pair. 
The last segment of the urus is keeled on its dorsal side. 
The peduncles of the last pair of uropoda are twice as long 
as the outer ramus. The outer ramus is much longer than the 
inner coalesced one. 
The head is more elongate than in the preceding species, 
not deeper than the pereion: The row of flat teeth consists 
of a broad frame-like margin extending from the sides of the 
head; the number of teeth is fourteen, occupying the whole 
space from the base of the antenn&e to the mouth. The row 
of teeth on the under-side of the head is also more prominent. 
