THE SPONGES OF THE WEST-CENTRAL PACIFIC 213 



U.S.N.M. No. 23140, My No. M. 524, collected September 16, 1949, by diver 

 in Tanapag Harbor, in northwest Saipan. The depth was 2 meters, and 

 the substrate was dead coral. This was not only the commonest, but it 

 was the only sponge in this portion of Saipan and was one of three species 

 occurring in this whole island. 



U.S.N.M. No. 23147, My No. M. 531, collected September 20, 1949, at the 

 extreme south tip of Guam from the lagoon inside Cocos Island, 

 known as Merizo Bay. The depth was 2 meters, and the substrate was 

 dead coral. This species was much more common there than other 

 sponges. 



The shape of this species is typically an erect wall or sheet. Many 

 specimens are deformed and have come to be regarded as massive; but if the 

 environment is at all favorable, the typical shape is assumed. The size is often 

 quite large, specimens up to 25 cm in height being found. The lateral dimen- 

 sions are usually a little less than this. The thickness of the sheet is often 

 about 3 to 6 cm. 



The color in life was bright golden orange, extremely conspicuous. The 

 consistency was mediocre. 



The surface is uneven, often covered with minute tubercles about 1 mm 

 high and 1 mm apart. The pores are about 50 p. to 140 jx in diameter and 

 sometimes are so close together that they are only 120 /.<. apart. More often, 

 however, they are several hundred fx apart. The oscules are very few in 

 number. The smaller specimens have none, but the larger specimens have 

 three or four apiece. These will be from 7 to 10 mm in diameter when fully 

 opened. 



The ectosome consists of a conspicuous dermis or cortex, very fine 

 grained and sometimes rather easily separable from the underlying endosome. 

 The thickness ranges from 50 /x to 1 mm. The nature of the endosome varies 

 some with the size and age of the specimen. The smaller, younger ones show 

 very little fibrous development ; but as they attain to greater heights, a larger 

 and larger percentage of the endosome is given over to fiber. In some of the 

 largest specimens these fibers reach a diameter of more than 1 mm. They are 

 somewhat dendritic in pattern, branching more often than anastomosing. The 

 meshes in places are quite small, even as little as 100 jx to 200 p, in diameter ; 



Text Figure No. 145. Spicules of Stylotella agminata, X 182. A: Tylostyle. B: Long, 

 thin style. C: Short, thick style. D: Probably a juvenile spicule. 



