HANSEN : THE ISOPODA. 99 



length, very slender ; the fifth joint almost as long as the second, somewhat 

 curved, very slender, and not expanded on its under side. Of the second, third, 

 and fourth pairs only the two proximal joints are not broken off. In the three 

 last pairs the fifth joint is almost twice as long as broad (Fig. 1 h), the seventh 

 joint (7) as long as the fourth, and very slender (in Figure 1 h all the hairs 

 are omitted). 



Abdomen. As long as the four posterior thoracic segments together, narrower 

 than the seventh segment, and decreasing in breadth from the anterior angle, 

 which is produced into a triangular acute process, turned forward and especially 

 outward. It consists of at least two visible segments — the posterior, of course, 

 consisting of fused segments — fused together, the anterior of which is short ; 

 besides, there is seen across the anterior part of the second segment a curved 

 transverse furrow, perhaps indicating a rudiment of a second articulation. In 

 the median line, just behind the furrow between the first segment and the rest 

 of the abdomen, is a small tubercle, especially obvious in a lateral view as a 

 rudimentary process. On the dorsal side are two deep longitudinal furrows, 

 at a considerable distance from each other, and anteriorly curving outward. 

 The posterior margin with three acute processes, the median one curved con- 

 siderably downward and much larger than the two others, each of which is 

 situated close inside the point where the dorsal furrow reaches the posterior 

 margin. The oblique terminal face of the abdomen is quite similar in both 

 sexes and rather peculiar (Fig. 1 a and 1 i) : the hind margin with the three 

 processes just mentioned, the oblique lateral margin a little arcuate, while 

 the infero-anterior margin is short and concave, the infero-lateral angle 

 being produced into a shorter process ; on the upper half of the terminal 

 face are seen the two oblong-triangular anal doors (Fig. li, d), and just 

 outside each door the uropod is attached. In the female the ventral oper- 

 culum (the first pair of abdominal limbs) has an impression along with and 

 somewhat inside of the lateral margin and close to the posterior margin ; in 

 the median line it possesses a keel, which somewhat before the middle is 

 produced into a rather long, moderately compressed acute process. In the 

 male the operculum (the first and second pairs of abdominal limbs together) is 

 represented in Figure 1 i, and scarcely needs a special description. (Having 

 but one male specimen, I omit the description of the " appendix masculina " 

 on the second limb.) 



Uropods (Fig, 1 i). Each consists of a moderately short and very slender 

 peduncle and two 1-jointed rami, the interior of which is about as long as the 

 peduncle and still more slender, the exterior one somewhat shorter. 



Size. A female specimen whose marsupium is still rudimentary (consisting 

 only of small plates on the second and fourth pairs of legs) is 28 mm. long and 

 11.2 mm. broad. Of the three females with the marsupium completely devel- 

 oped (in two specimens filled with eggs) the largest is a little smaller than the 

 specimen with rudimentary marsupium ; the smallest is 23.3 mm. long and 

 9.8 mm. broad. The youngest female is 20.3 mm. long ; the male is about 

 24.5 mm. long and 10 mm. broad. 



