THE SPONGES OF THE WEST-CENTRAL PACIFIC 147 



D 



Text Figure No. 94. Spicules of Microciona placenta, X 782. A: Tylostyles. B: Basal 

 portion of one of the styles. C: Echinating acanthostyle. D: Side view of one of the 



isochelas. 



by 122 ix to 5.5 fx by 270 fx. There also are echinating spicules which are 

 acanthostyles, 5 [x by 67 /x. These are not common. Microscleres consist 

 of palmate isochelas 13 /x long and also are relatively uncommon. 



Lamarck, 1814, page 374, described Spongia placenta from the Aus- 

 tralian region, and Topsent, 1931, page 24, refers it to the genus Wilsonella, 

 redescribing it capably. The genus Wilsonella, however, is characterized by 

 having arcuate rather than palmate isochelas, and the species placenta there- 

 fore is transferred to Microciona. Agreement of this specimen from Truk 

 with the Australian species is remarkably close, to judge from published de- 

 scriptions, although Lamarck's specimen grew to somewhat lamellate shape. 



GENUS AN A AT A de Laubenfels 

 Anaata lajorei, new 



Text Figure No. 95 



This species is here represented by the following : 

 U.S.N.M. No. 22827, My No. M. 102, here designated as type, collected 

 June 11, 1949, by hand while wading at Ailing-lap-lap Atoll in the lagoon 

 near Bikajela Islet in the southern portion of the atoll. The depth was 

 just below low tide mark, and the substrate was dead coral. 



This is an incrusting species, measuring less than 1 mm thick and spread- 

 ing laterally indefinitely. 



The ectosome and endosome color in life was black, and the consistency 

 mediocre. 



The surface is smooth and lipostomous. 



There is no sharp differentiation between ectosome and endosome. 



The skeleton consists principally of large smooth styles placed with 

 their bases towards the substratum and their points outward, 2 /x by 220 [x 

 to 3 /a by 240 jx in dimensions. Among them, probably to be regarded as 

 echinating, are acanthostyles, 3 /x by 135 /x to 4 \x by 80 p.. The smaller they 

 are, the more they are completely spined. The larger ones are spined chiefly 

 near the head. The microscleres consist of arcuate isochelas, 20 jx long. 



