PORTO RICAN ISOPODA. 
175 
The feet of this species, as in the typical species described by Dana, are in two series. The first 
is composed of the first, three pairs of feet, which are comparatively stout and increase in length to the 
third segment. The second series begins on the fourth segment with a pair of short feet which fold 
transversely; the other pairs are successively longer and fold backward. The feet of the second series 
are much more slender than those of the first. The dactvli of all are biungulate. The carpal and 
propodal joints are spinulose beneath. 
The operculum is not traversed by an oblique line. The sides of the basal segment are subparallel. 
The terminal segment is about as broad as long. 
The above is the original description, to which I wish to add that the fourth pair of legs consists 
of but six segments, the ungual joint being absent. 
From Mayaguez and Vieques. Largest specimen, 14 by 2.5 mm.; smallest, 6.5 by 1.6 mm. 
Tribe ONISCOIDEA. 
LI GUILE. 
Ligia gracilis, new species. 
Body elongate-ovate, rather narrow; about 2.75 times as long as broad. 
Head about 2.5 times as broad as long, breadth about two-thirds of greatest width of body, 
rounded in front, bilobate posteriorly. First segment of thorax longest, the next five subequal, the 
last somewhat shorter; first segment with front margin excavated to receive lobes of head, which, on 
account of their convexity, appear to overlap it, produced beneath the eyes at anterior lateral angles; 
second, third, fourth, and fifth segments of about equal breadth; posterior margins of first, second, and 
third segments nearly straight; fourth segment somewhat produced at posterior lateral angle, the last 
three segments strongly produced to acute angles; seventh segment with posterior margin excavated 
dorsally so as to uncover the first segment of pleon. 
Abdomen constituting about one-third of total length of body; first two segments short and 
narrow, the postero-lateral angles not produced; first segment (sometimes the second) hidden laterally 
by the angle of the last thoracic segment; third segment widest, the next two successively narrower 
and longer, all three strongly produced at postero-lateral angles; telson about three-fourths as long as 
broad, with a sharp tooth at postero-lateral angle and 2 blunt, rounded teeth inside of it on each side; 
in the median line there is a blunt angle, but no sharp tooth, as in L. olfersii and L. exotica. 
The lateral borders of all of the thoracic and abdominal segments are fringed with minute teeth. 
Eyes large, black, lateral, strongly convex, facets small, numerous; first antennae minute, 3-jointed; 
second antennae, when folded back along sides of body, reaching to about end of thorax; peduncle 
5-jointed, first two joints short, subequal, last three successively longer, flagellum about 1.5 times as 
long as peduncle, consisting of about 37 joints. 
Mandible without palp, with two apical plates armed with three teeth each, and a dentate plate 
on internal face. Molar surface beset with small setae around its base, a row of large plumulose seta’ 
around base of inner dental lamella. 
First maxillae with plate of first joint furnished with three stout plumulose spines and a tuft of 
slender hairs, third joint with stout spines; second maxilla with one large plate and a shorter, more 
slender one; maxillipeds broad, with a 5-jointed palp, bearing setae on its inner edge and stout spines on 
outer edge and ventral face; plate of second joint furnished with many short crowded spines and setae. 
The thoracic legs increase in length from first to last; in all, the terminal joint is short and biun- 
gulate, the sixth or penultimate joint is long, and in the last pair of legs the sixth and seventh joints 
together equal or slightly exceed the fourth and fifth combined; all of the legs are more or less spiny 
in all of their joints. 
The uropods are biramous, the inner ramus being about twice as long as the peduncle; outer 
ramus broken. 
Ten specimens from Oulebra, under alga; and drift alongshore. Largest specimen, 15 by 5.5 mm.; 
smallest, 5 by 1.5 mm. 
