24 STALK-EYED CRUSTACEA. 
The tooth formed by the projecting inner orbital angle does not attain the 
level of the frontal teeth, and it is double, the orbital margin just outside of 
it being slightly folded, raised, and projected forward so as to form a secon- 
dary tooth similar to that in A. spinimanus, but not so well-marked. The 
antero-lateral margin of the carapace is nine-toothed, including the tooth at 
the outer orbital angle; the posterior tooth is hardly larger than those in 
front of it; the posterior margin of these teeth is convex. The anterior 
edge of the merus of the chelipeds is armed with five spines. The carpus 
has an internal and a smaller external spine. There is a spine on the pro- 
podus at the base at the point of articulation with the carpus, and another on 
the upper margin a little distance back of the articulation with the dactylus. 
The distal edge of the fifth pair of legs is spinulose. 
Length, 25 mm.; breadth, 39 mm.; length of merus of cheliped, 24 mm.; 
length of propodus, including digit, 83 mm.; length of internal carpal spine. 
measured from distal margin of carpus, 3.3 mm. 
Station 3379. 52 fathoms. 5 males, 4 fem. 
ea 590: 00 ae 1 male. 
A large number were also taken in the tow-net on the surface at the 
following stations : — 
Off Mala Point, Hydr. 2627, 3355, 3371, 3382, 3386, 3398, and 50 miles 
south of Guaymas. 
The specimens taken at the surface are small, and much darker in color 
than those that came up in the trawl, but they show no structural differences. 
I take them to be the same species in the pelagic stage of its existence. 
This species is related to Achelous depressifrons Stimps., from the Atlantic 
side of the Continent. Compared with A. depressifrons it is broader, and 
the curve formed by the front and the antero-lateral margin of the carapace 
forms an are with a longer radius; the lateral lobe of the front is broader ; 
the tooth of the inner orbital angle is double, as above described; the teeth 
of the antero-lateral margin have broader bases, and the anterior one at the 
outer orbital angle is not so prominent; the protuberances on the cardiac 
and branchial areas are less prominent; the internal carpal spine is shorter, 
and the distal margin of the merus of the fifth pair of legs is denticulate 
behind the articulation of the carpus. 
