34 



MARINE ISOPODS FROM THE PHILIPPINE ISLANDS. 



Bonnier there are no dorsal bosses. In Tylohepon Stebbing there are bosses on the 

 last two thoracic segments, but that of the sixth segment is trifed. In Scyracepon 

 Tattersall there are six bosses, one on each of the last six segments of the thorax. In 

 Cardicepon Nobili there is one large median boss on the sixth thoracic segment. 



This genus is closer to Scyracepon Tattersall than to any of the other genera men- 

 tioned. It differs, however, from that genus, in having but three median dorsal 

 bosses on the thorax of the female, in having the outer branches of the first pair of 

 pleopoda leaf-like and much larger than any of the other branches, and in having the 

 abdomen of the male distinctly segmented. 



The type of the genus is Merocepon xanthi, new species, the description of which 

 follows. 



Merocepon xanthi, sp. nov. 



Body of adult female ovate, rather asymetrical in outline. Color, in alcohol, yellow. 



Head large, bilobate in front, and surrounded, except in the posterior part, by a 

 wide border, wider at the sides than in front. Eyes absent. The antennae are situated 

 on the ventral side and are not visible in a dorsal view; the first pair are minute and 

 seem to be composed of two articles; the second pair are composed of three articles. 



a b d 



Fig. 31.— Merocepon xanthi. a, Female, X16; b, male, X 27 J; c, abdomen of male (underside), X 41; d, 

 first lamella of marsupium," X20^. 



The seven thoracic segments are equal in length in the middle of the dorsal region. 

 The second, third, and fourth have large pleural bosses, rounded and with a small 

 depression in the center. Lateral to these pleural bosses, which are very prominent 

 and conspicuous, are the pleural lamellae of the segments. The pleural bosses are not 

 present on the first or the last three segments. The last three segments have each a 

 median dorsal boss, that of the sixth segment being the largest, and that of the 

 seventh somewhat hook-shaped. 



The first five segments of the abdomen have pleural lamellae in the form of long, 

 narrow appendages, with tuberculiform margins. The five pairs of pleopods are 

 double branched, with the outer branches elongate and similar to the pleural lamellae 

 of the abdominal segments with the exception of the first, which are leaf -like; the 

 inner branches are small and difficult to see. The uropoda consist of a pair of elongate 

 lamellae similar to the pleural lamellae of the abdomen. 



The marsupial plates are large, bounding a large cavity, and overlapping on the 

 ventral side so as to completely cover the eggs. The seven pairs of legs are small and 

 feeble. 



