10 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Chasmocarcinus cylindricus, sp. nov. 
Length of carapace less than three-fourths its posterior width. Fronto-orbital width about half 
width of carapace. Carapace subcylindrical, almost level from side to side. Anterior half of lateral 
margin marked by a sharp granulated line. Sutures visible about cardiac region. At inner angle of the 
branchial region there is a depression from which various shallow wrinkled furrows radiate. Surface 
covered with a short pubescence. Front a little wider than either orbit; margin subtruncate, upper 
surface with a median depression, which in a dorsal view makes the margin appear bifid. Margin of 
orbit concave, directed obliquely outward and a little forward. Right chel®ed larger than the left. 
Carpus with inner angle rounded, and without a tooth. Manus of larger cheliped about one-half wider 
than that of smaller in the male, and much more swollen, its fingers gaping at base; in the female the 
hands are more nearly equal and the fingers do not gape. Ambulatory legs narrow, fringed with hair. 
The following are the dimensions of two specimens: 
Locality. 
Sex. 
Length. 
Width. 
Fronto- 
orbital 
width. 
Station 6061 
Male 
4.6 
6.5 
3.5 
Station 6059 
Female 
6.7 
9.5 
4.7 
This species is distinguished at a glance from the three previously described, by its broader and 
more cylindrical carapace. 
(c) Abdomen of male, x 4. (d) Abdomen of female, x 4. 
Type locality, Mayaguez Harbor, Porto Rico, 12 to 18 fathoms, sand, mud, station 6061, 4 males, 
2 females (Cat. No. 23765). Other Porto Rican localities are off Aguadilla, 137 fathoms, sand, mud, 
and shells, station 6055, 1 female; Mayaguez Harbor, 7 fathoms, sticky mud, station 6051), 1 female; 
Mayaguez Harbor, 75 to 76 fathoms, rocky, sand, and coral, station 6063, 1 male, 3 juv. ; Mayaguez 
Harbor, 161 to 172 fathoms, sand, mud, station 6066, 2 males, 2 females. 
Genus SPEOCARCINUS Stimpson. 
Spencarcinus Stimpson, Ann. Lye. Nat. Hist. N. Y., vii, 58, 1859. 
Carapace longitudinally convex, almost semicylindrical, transversely nearly flat; posteriorly 
narrowing very little, anteriorly margins arcuate and dentate. Front less than half the width of cara- 
pace. Orbits marginal, oblong, eyes movable. Outer maxillipeds moderately separated from each 
other; merus subquadrate, with a notch at antero-internal angle for the insertion of palpus. First two 
abdominal segments narrow, exposing largely the sternal segment; third segment much wider, but 
still not extending to coxal joints of legs; third, fourth, and fifth segments coalesced. Chelipeds short, 
thick. Ambulatory legs narrow, smooth, compressed; dactyli long, ciliate. 
