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. spinunanits, but not so well-marked. The 

 antero-lateral margin of the carapace is nine-toothed, including the tootli 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, 33 mm. ; length of internal carpal spine, 

 measured from distal margin of carpus, 3.3 mm. 



Station 3379. 52 fathoms. 5 males, 4 fem. 

 " 3390. 56 " 1 male. 



A large number were also taken in the tow-net on the surface at the 

 following stations : — 



Ofr 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 diflferences. 

 I take them to be the same species in the pelagic stage of its existence. 



This species is related to Achelons dcjpressifrom Stimps., from the Atlantic 

 side of the Continent. Compared with A. deprcssifrom it is broader, and 

 the curve formed by the front and the antero-lateral margin of the carapace 

 forms an arc 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 ba.ses, 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. 



