216 UNITED STATES NATIONAL MUSEUM BULLETIN 251 



Marianas Islands : Saipau ; lagoon west of island, 500 yds. NNE. of Managaha 

 Island ; P. E. Cloud, loc. 4. One specimen 7 mm. long ( USNM 11503) . 



Wake Island : C. H. Edmondson, sta. 607. Three specimens 9 to 10 mm. long 

 (USNM 11760).— C. H. Edmondson, sta. 608. Three specimens 12 to 13 mm. 

 long (USNM 11761). 



Description. — Six specimens (9-13 mm. long) from Wake Island, 

 one specimen (7 mm. long) from Saipan Island, and a single 10 min. 

 long specimen from the Palau Islands were examined. Animal roughly 

 spherical or elliptical in shape, usually attached to substratum by 

 right ventral side. Both siphons distinct in Palau specimen, but 

 nearly sessile on others more or less contracted. Branchial siphon sub- 

 terminal, atrial subterminal or situated near middle of dorsal side; 

 apertures 4-lobed, separated from each other by about half of body 

 length. Test leathery, thin but very tough; coloration varies from 

 yellowish white to yellowish brown or grayish brown in preserved state, 

 inner surface whitish with pearly glistening ; surface originally smooth 

 but generally irregularly wrinkled in contracted specimens, especially 

 areas around apertures furnished with small irregularly shaped swell- 

 ings. Mantle reddish brown to dark reddish, rather thin, although 

 dorsal side may be thickened considerably in some specimens. Fine 

 villus-like protuberances on atrial velum and also on proximal inner 

 surface of siphons. Distal inner surface of siphons covered with 

 many minute spinules. 



Six branchial plications in smaller specimens and seven to eight in 



larger ones. Inner longitudinal vessels arranged (D = dorsal, V = ventral) : 



7 mm. long specimen (from Saipan) 



Left D 1 (11) 1 (6) 1 (10) 1 (10) 1 (8) 1 (4) 1 V 



Right D 1 (10) 1 (6) 1 ( 9) 2 ( 9) 2 (7) 1 (6) V 



10 mm. long specimen (from Palau) 

 Left D 1 (12) 1 (9) 1 (13) 2 (11) 1 (9) 1 (6) 1 V 

 Right D 1 (13) 1 (7) 1 (13) 2 (12) 1 (9) 1 (8) 1 V 

 12 mm. long specimen (from Wake) 

 Left D 1 (15) 1 (13) 1 (16) 3 (12) 2 (11) 2 (7) 1 (3) V 

 Right D 1 (13) (12) 1 (14) 1 (13) 1 (14) 2 (8) V 



12 mm. long specimen (from Wake) 



Left D 1 (15) 1 (12) 1 (15) 2 (13) 2 (11) 1 (7) 1 (3) 1 V 

 Right D 1 (11) 1 (11) 1 (17) 2 (13) 2 (12) 2 (8) 1 (4) V 



13 mm. long specimen (from Wake) 



Left D 2 (17) 1 (11) 2 (17) 2 (14) 2 (11) 1 ( 9) 1 (8) (6) V 

 Right D 2 (14) 1 (13) 2 (17) 2 (13) 3 (10) 2 (10) 1 (6) V 



Ventralmost fold may be rudimentary in some specimens. Trans- 

 verse vessels found in following arrangement : 1p2p1,1p2p2p2p1, 

 orlp3p2p3pl (numerals indicate orders of thickness of vessels, p 

 represents parastigmatic vessel). Stigmata elongated, generally 3 to 5 



