230 
THE YOYAGE OF H.M.S. CHALLENGER. 
Bathyplax, A. Milne Edwards. 
Bathyplax, A. Milne Edwards, Bull. Mus. Comp. Zool., vol. viii., No. 1, p. 16, 1880. 
In this genus the carapace is slightly transverse, longitudinally convex and finely 
granulated on the dorsal surface ; the branchio-cardiac sutures are distinct. The 
antero-lateral margins are arcuated and armed with two spines (the hepatic and lateral 
epibranchial spines). The front is deflexed, and is more than one-third the width of the 
carapace ; its straight anterior margin projects over the bases of the antennules. The 
orbits are very small and rudimentary. The epistoma is very narrow and transverse. 
The longitudinal ridges of the endostome or palate are rather indistinctly defined in the 
specimens I have examined. The post-abdomen of the male is short, distinctly seven- 
jointed, and occupies at the base the whole width of the sternum between the bases of the 
fifth ambulatory legs. The eye-peduncles are very short and nearly immobile, and the 
cornese in the typical form are not developed. The flagella of the antennules are 
elongated and transversely plicated. The basal antennal joint is much larger than the 
next joint, and reaches the infero-lateral process of the front; the elongated flagella arise 
from within the interior hiatus of the orbits. The exterior maxillipedes are short, and 
their exognath is rather broad ; the ischium of the endognath is not produced at its 
antero-internal angle ; the merus is distally truncated ; its antero-external angle is not 
produced, and its antero-internal angle, where the next joint articulates, is emarginated. 
The chelipedes are dissimilar and of moderate length ; the merus is short, trigonous, with 
a spine on its superior margin, and it has on the inner surface a transverse stridu- 
lating ridge near the distal extremity ; the carpus has a spine or tubercle on its inner 
surface ; the palms are short and compressed, and the left palm (but not the right) has 
lobe or tubercle on the inner surface, near the superior margin; the dactyli are com- 
pressed, dentated on the inner margins, and distally acute. The ambulatory legs are 
slender and somewhat elongated ; their dactyli styliform and straight. 
Of the single species described there is in the Challenger collection an interesting 
variety which I have designated — 
Bathyplax typhlus, var. oculiferus, nov. (PI. XX. fig. 3). 
cf. Bathyplax typhlus, A. Milne Edwards, Bull. Mus. Comp. Zool., vol. viii., No. 1, p. 16, 
1880. 
South of Pernambuco, off the coast of Brazil, in 30 to 400 fathoms (Stations 122 
to 122c), lat. 9° 5' 0" to 9° 10' 0" S., long. 34° 49' 0" to 34° 53' 0" W. (An adult 
female bearing ova.) 
