POLYCHELES NANUS. 121 
Polycheles nanus (Smrrn). 
Plate XXXIV, Fig, 1°, 7°. 
Pentacheles nanus Smit, Ann. Rep. U. 8. Fish Comm. for 1882, p. 359, 1884; id. for 1885, p. 651, 
Plate VII. Fig. 1, 1*, 1886. 
Station 3362. 1175 fathoms. 2 fem. 
<> 3380. 899 & 1 fem. 
‘ da92., 1270 a 3 males, 3 fem. (1 ovig.). 
cc Ss«£83393. 1020 & 1 fem. 
«8400. = 1322 © 6 fem. (1 ovig.). 
These specimens differ slightly, but constantly, from the type specimens 
from the Atlantic. The edges of the suleated carina on the sixth abdomi- 
nal somite are less prominently denticulated and the tubercle at the posterior 
end of this carina is lower. Further, the spine near the base of the dorsal 
surface of the telson of the type specimens is reduced to a blunt tubercle in 
the Pacific examples. In these regards, the Pacific form resembles P. sculp- 
tus, adding weight to Professor Smith’s suggestion that P. nanus may be only 
a dwarf deep-water variety of P. seulptus. 
An adult ovigerous female measures 58 mm. in length; carapace 24.5 
mm. by 16.5 mm. 
The posterior thoracic appendages are chelate in both sexes. 
The branchial formula is as follows : — 
Somites Wage =10-¢ Xe XeT Xie XIU) XLiVs 
Pleurobranchie 0 0 0 1 1 1 1 — A: 
Arthrobranchie 0 0 2 2 2 2 0o= 8 
Podobranchize 0 0 1 1 il 1 Of—— 4. 
Epipods 0 r r fi r r on (57) 
“16+ (57) 
The epipods of the tenth to the thirteenth appendages are represented 
merely by a plate-like expansion of the base of the stem of the podo- 
branchia. The epipod of the third maxilliped is very minute and bears 
no true gill. The podobranchia and the two arthrobranchie of the tenth 
somite (cheliped) are much reduced in size. 
16 
