PORTO RICAN ISOPOD A. 
173 
The free abdominal segment is broader and wider than the last thoracic segment, with two or 
three furrows at the sides; on its posterior border are three low processes, from a crater in the top of 
each of which a tuft of setae projects. The telson has three prominent processes projecting backward 
from its base, the central one with a tuft of setae. At the base of the apical incision there is a broad 
rounded process. The apical notch is furnished with four teeth, two small ones at the base and two 
larger ones outside of them and at a slightly lower level. The two limbs forming the borders of the 
notch are notched at their tips and furnished with a tuft of seta;. 
The uropods have a long, curved outer branch. The posterior part of telson and the uropods are 
covered with very short, close-set soft hairs and scattered tufts of longer ones. Most of the body is 
minutely tuberculate, with scattered tufts of two or three setae. The epistome is broad, pointed in 
in front and widely forked behind, the two limbs embracing the clypeus. 
First antennae have a 3-jointed peduncle, first joint long, stout; second joint deeply embedded in 
first; third joint as long as second, slender; flagellum 11-jointed, setose, about as long as peduncle; 
second antennae extending to about end of third segment; peduncle 5-jointed, slender; flagellum 14- 
jointed, a little longer than peduncle. Mandible with cutting edge, molar surface and palp. .Maxil- 
lipeds with 5-jointed palp, of which the last is slender and the second, third, and fourth strongly 
produced internally; plate of second joint broad, with hooks and terminal spines. Thoracic legs 
increasing in length posteriorly, more or less setose, terminal joint biangulate. 
Female smaller, resembling male in head and thorax. First joint of abdomen without tubercles; 
basal processes of telson small, no process at base of apical incision; apical incision small, simple, 
rounded, without teeth; outer ramus of uropods lamellar, inner ramus well developed, lamellar, fused 
to peduncle. 
From coral reefs at Mayaguez, Boqueron Bay, Puerto Real, Arroyo, and Fajardo. Largest male 
7.5 by 3.5 mm. Largest female 4.8 by 2.3 mm. Color in life, red or pink. 
The smaller form was described as Cymodocea burmudensis by Ives, who at first suspected that it 
was the female of the other, but concluded otherwise upon finding male organs upon one specimen. 
In Porto Rico the two were always found associated and as all the larger forms were found to be males, 
while none of the smaller ones could be so determined, I am inclined to believe that Mr. Ives’s speci- 
men was an anomaly. The two forms agree in all particulars save only those which are generally 
recognized to be sexual. 
The form described by Miss Richardson as Dynamenc nodulosn is probably the female of Cilicea 
caudata gilliana Richardson, or of a related species. 
Dynamene perforata, new species. 
Body stout, about twice as long as broad, slightly increasing in breadth posteriorly, sides almost 
straight. Head short, broad, a little over half as wide as greatest width of body (about 3.5 times as 
broad as long). First thoracic segment longest, about equal in length to head; last thoracic segment 
shortest, about half length of first; other five segments equal, about two-thirds as long as first; first 
segment strongly excavated near sides to receive the eye lobes of posterior margin of head, anteriorly 
produced at lateral border to an acute process beneath the eye. 
The lateral margins of all of the thoracic segments are somewhat produced posteriorly, the poste- 
rior edge being grooved to slide over a ridge on the outer anterior margin of the succeeding epimeron 
when the animal rolls into a ball, the segments thus locking against a transverse stress; the epimeron 
of the last segment, which in the male is longer than the others, is without this groove, but it slides 
outside of a forwardly projecting process or lug. The lateral margin of the first segment is long and 
straight, of the second, third, and fourth is narrower than the dorsal length, the fifth, sixth, and 
seventh broader and more rounded, the latter being more distinctly produced behind the posterior 
dorsal margin of the segment, especially in the male, where it forms a large epimeral plate. 
Free joint of abdomen a little less than one-third length of telson, produced into a posteriorly 
projecting process over lateral margin of telson, at base of process a lobe crossed by a suture, indicating 
probably two of the fused segments which constitute the free abdominal segment. 
Telson in male triangular, notched posteriorly; in front of notch a groove in median line connect- 
ing with a transverse foramen. This region varies in different individuals; in some the groove is shal- 
low, and in some it is deep, and in one it is clearly an incision connecting the terminal notch with the 
