480 REVISION OF TTIE AXIKELLIJ)^, i., 



exists in spiculation between the present species and T. 

 diyitatus var. strouyylatus, — the only definitely definable ehai'- 

 acter justi£yin,(f their inclusion in the present species, rather than 

 in T. diyitatns, is the elongate tapering habit of their branches. 

 Among the remaining specimens, however, there is one which in 

 various respects stands considerably apart from all the rest, and 

 in these respects also is by far the must divergent fi-om 7'. dii/ifa- 

 fufi. I therefore select this specimen to represent the typical 

 form of the species, and the remainder I refer pi'ovisionally to an 

 undesignated variety, leaving the problem of their correct alloca- 

 tion to be determined in the future. 



T. RETEPOROSUS, typical form. 

 (PI. xxi., fig.'2: PI. xxiii., fig.5; PI. xxiv., fig.3; PI. xxvi., figs. 1,4,7; 



PI. xxvii., fig.5. 

 The single, excellently preserved specimen (PI. xxi., fig. 2), — 

 whicli measui'es 340 nun. in total height — consists of a half-score 

 of long, lax, straight, gi-adually tapered, main branches (160 to 

 250 mm. in length), arising dichotomously and sub-dichotomously 

 within a comparatively short distance of the short stalk, and of 

 about the same number of shorter (10 to 120)um. long), but 

 other\\ise similar, sporadically occurring secondary branches. 

 But for overlapping and occasional sliglit torsion, the branches 

 would be disposed in a single plane, and the habit of the sponge 

 tiabellate. The branches, in addition to tapering distally, are 

 also more or less narrowed proxiinally (attaining their maxinuun 

 stoutness usually at some considerable distance above their base), 

 and, with the excep'tion of a few of the shorter ones, are gener- 

 ally more or less compi'essed in the plane of branching; the 

 stoutest measure at most 12 or 13 mm. in the major diameter of 

 their cross-section, and 9 to 10 mm. in the direction at right 

 angles thereto. Anastomosis between the branches does not 

 occur. The oscula, which measure up to 075 mm. in diameter, 

 are arranged almost exclusively, though not always very regu- 

 larly, in two longitudinal series situated on opposite sides of the 

 branches, or occasionally in a single longitudinal series. The 

 surface is smooth and even, without the faintest trace of granu- 



