MUSEUM OF COMPARATIVE ZOOLOGY. 155 
Family PORTUNIDZ. 
Achelous affinis, sp. nov. 
Carapace moderately convex both longitudinally and transversely, the frontal 
region depressed, horizontal; surface rugose, granular, and pubescent. Front | 
not prominent, composed of four blunt teeth, not counting the internal angle ; 
of the orbit; the two teeth near the median line are equilaterally triangular, 
separated from one another by a triangular notch ; the next teeth on the outer 
side are separated from those within by a shallow sinus, and fall off abruptly 
on the outer side into a deep notch which separates the front from the inner 
orbital angle. The two middle teeth of the front are a trifle longer than the 
lateral teeth. The tooth formed by the projecting inner orbital angle does not 
attain the level of the frontal teeth; it is double, the orbital margin just out- 
side of it being slightly folded, raised, and projected forward so as to form 
a secondary 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 propodus 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 merus of the fifth pair of legs is spinulose. 
Length, 25 mm.; breadth, 39 mm.; length of merus of chelipeds, 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 females. 
«< - 3390. -56 “ 1 male. 
A large number were also taken in the tow-net at the surface at the follow- 
ing stations: Off Mala Point; Hydr. 2627; Nos. 3355, 3371, 3382, 3386, 
3398 ; 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 show no structural differences. I take 
them to be the same species in the pelagic stage of its existence. 
This species is very closely related to Achelous depressifrons Stimps., from the 
Atlantic side of the continent. Compared with 4. 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 bran- 
chial 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. 
