134 
BULLETIN OE THE UNITED STATES FISH COMMISSION. 
Petrolisth.es tridentatus Stimpson. Plate 3, fig. 2. 
Petrolisthes tridentatus Stimpson, Annals Lyc.Nat. Hist. New York, vn (March, 1859), p. 75, pi. i, fig. 4. 
The rostral lobe of the front is broad and triangular, the lateral lobes or teeth are well separated 
from the median lobe and markedly divergent. The chelipeds are large, glabrous to the eye, 
minutely rugose under a lens. There are no teeth or spines anywhere, with the exception of a rounded 
tooth on the inner distal angle of the merus and a small sharp, curved spine on distal angle of carpus. 
The inner margin of carpus is thin and slightly produced; outer margin marked with enlarged rugie. 
P. tridentatus has been taken at St. Thomas, Barbadoes (types), and Trinidad. 
Petrolisthes mar ginatus Stimpson. Plate 3, fig. 1. 
Petrolisthes marginatus Stimpson, Annals of the Lyceum of Nat. Hist, of New York, vn (1859), p. 74. 
The outline of the front from the median lobe to the angle of the orbit is straight; the median 
lobe is rounded and deflexed. The carapace is pubescent. The chelipeds are not so slender as in 
P. armatus; there are four sharp teeth on the inner margin of the carpus; in the center is a row of small 
round tubercles; a row' of more flattened tubercles arm the outer margin. A ridge runs from the gape 
of the fingers to the anterior angle of the carpus; the low'er margin of the hand is armed with spinules. 
The color of the specimen when it first reached the Museum was pink. Stimpson gives the color as 
‘ 1 a deep purplish crimson. ’ ’ The ambulatory feet were lost from the single specimen. Taken at Ponce. 
Petrolisthes quadratus, new species. Plate 3, fig. 4. 
The front is thin, produced to an angle in the middle. A deep depression reaches the apex from 
between the protuberances of the gastric region ; the orl fits are raised and a depression extends to the 
inner angle of the orbit from a point at the side of the gastric protuberances. There is a small protuber- 
ance on the gastric region behind the eye. There is only a slight emargination of the carapace where 
the cervical groove meets the side. The sides of the carapace are parallel; near the margin there are 
rugose lines, becoming coarser on the shoulder. The rneral segments of the ambulatory feet are rugose; 
there are no spines anywhere except under the dactyl. The right cheliped is wanting; the left is 
large and strongly granulated. There are two slight longitudinal depressions and three resulting 
ridges on the carpus; the marginal granules are a little enlarged. There is a sulcus on the movable 
finger and a slight one near the crest of the palm. The fingers are pubescent on the inner surface near 
the prehensile edges. There are no spines or teeth on the chelipeds. 
Reefs at Ponce. One specimen. Length of carapace, 5 m.; width, 5.5 mm. 
Petrolisthes nodosus Streets. 
Petrolisthes nodosus Streets, Proc. Acad. Nat. Sci. Phila., xxiv, p. 138, 1872. 
The following is from the original description: “The carapace is broadly ovate, about as broad as 
long. The anterior portion is nodulated; the nodules are arranged in a semicircular manner trans- 
versely across the dorsum from one hepatic region to the other. The posterior portion of the carapace 
is distinctly imbricated. The front is prominent and deeply tridentate; the middle tooth is the largest 
and triangular in shape and very slightly more prominent than the lateral ones. The carpus is shorter 
than the hand. The anterior margin is arihed with four large, serrated, and imbricated teeth; the two 
middle ones'are the largest and are united at their bases; the external tooth is smallest.” 
Petrolisthes jugosus Streets. 
Petrolisthes jugosus Streets, Proc. Acad. Nat. Sci. Phila. 1872, p. 134. Kingsley, Proc. Acad. Nat. Sci. Phila. 1879, p. 405. 
The carapace is about as broad as long; the front is evenly convex from orbit to orbit when seen 
from above; in front it shows a V-shaped depression on the median line. The cervical groove is 
strongly marked; there is a paired tubercle on the side of the gastric region formed in part by a 
depression between this point and the raised margin of the orbit. The chelipeds are rather short for 
the genus; the carpus has a U-shaped sulcus on its upper surface; the opening of the U is on the 
proximal end; the ridge within the U and the ridges on each side are crossed diagonally by numerous 
raised lines; the anterior margin is armed with four teeth graded in size, the largest being on the 
proximal end. The hand is roughened with rather coarse granules; the lower margin is carinate. 
The collection contains several specimens which I refer to this species; they are specifically 
identical with Mr. Kingsley’s specimen from Key West, with which they have been compared. The 
Museum collection contains a number from St. Thomas. The Porto Rico expedition obtained several 
specimens at Oaballo Blanco Reef and at Ponce. 
