154 



GEODIA MESOTRIAENELLA. 



and as they are exceedingly scarce in the spicule-preparations, I am by no 

 means sure that they are proper to the sponge. A correlation between the 

 ray-number and the size of the spicule is not clearly discernible. 



The large oxysphaerasters have a spherical centrum, 6-9 n in diameter, 

 from which from fifteen to twenty-three regularly distributed rays arise radially. 

 The rays are straight, conical, sharp pointed, 6-7 long and 2-2.5 /i thick at 

 the base. Each ray bears a small number, sometimes only one or two, vertically 

 arising spines. The whole aster is 20-21 /t in diameter. 



The diameter of the centrum of the small strongylosphaerasters (Plate 34, 

 fig. 26) is 1.6-4.5 /i, usually from a quarter to a half of the diameter of the whole 

 aster. From this centrum generally from ten to seventeen regularly distributed 

 rays arise radially. Very rarely strongylosphaerasters with fewer (one or three), 

 or with more numerous (up to twenty-five) rays have been observed. The rays 

 are cylindrical or cylindroconical and truncate. In the strongylosphaerasters 

 with small centrum (Plate 34, fig. 26a) the rays are much longer than thick and 

 attenuated towards the end. In the strongylosphaerasters with large centrum 

 (Plate 34, fig. 26b) the rays are only twice as long as thick or even shorter, and 

 cylindrical. The rays are covered with spines, which are larger in the one- and 

 three-rayed than in the many-rayed forms. The ray of the one-rayed strongylo- 

 sphaeraster is 7.2 ji long and 2 /jl thick; the rays of the three-rayed forms are 

 4-5 ft long and 1 /( thick; those of the many-rayed forms are 2-4.5 p. long and 

 0.5-1 /I thick. The total diameter of the aster is 6-11 /(. The ray-number is 

 in so far in inverse proportion to the size of the spicule as the one- and three- 

 rayed forms are 8.4-11 /x, the forms with more rays 6-10 /x in total diameter. 



The sterrasters (Plate 34, fig. 23) are flattened ellipsoids, usually 87-97 //, 

 rarely as much as 107 ^long, 77-86 /t, rarely as much as 92 /i broad, and 58-69 pi 

 thick. The proportion of length to breadth to thickness is, on an average, 

 . 100:89:71. 



This sponge was caught with the tangles at Station 4417 on April 12, 1904, 

 near Santa Barbara Islands, S. W. rock Santa Barbara Island, N. 8° W., 

 11.7 km. (6.3 miles), drift S. 73° W.; depth 53 m. (29 f.); it grew on a bottom 

 of fine yellow sand and coralline rock. 



The cribriporal character of the afferent and efferent apertures and the 

 ellipsoidal sterrasters show that this sponge belongs to Geodia. It is most 

 closely allied to the sponges described by Dendy (1905) as Geodia ramodigitata 

 Carter and G. areolata Carter, and to those described here as Geodia ataxastra, 

 G. breviana, G. agassizii, and G. mesotriaena. In Dendy's Geodia ramodigitata 



