270 SIDNEY F. HAKMER. 



iiiterveiiino;- slight depressions between the longitudinal rows. 

 The back bears a moderate number of short cylindroid 

 calcareous papilhe. These are much more definite structures 

 than the irregular outgrowths found on the back of many 

 encrusting species which grow on irregular surfaces, Home 

 of them have a rounded termination, while others are trun- 

 cate ; this truncation suggests that the papillae may be con- 

 tinued into cliitinous rootlets, and one or two of the (dry) 

 specimens appear to show remains of these rootlets, which 

 are, however, much more delicate than those of the typical 

 form of S. neozelanica. 



The edge is thin and much raised, passing gradually into 

 the post-oral slielf, which is usually very narrow, especially 

 proximally, though of considerable depth, and commonly 

 slopes gradually into the cryptocyst. The oral shelf is 

 narrow or vestigial in a zooecia, but of great horizontal 

 extent in the b forms, where it is finely tubercnlated, flat or 

 concave above, its free edge somewhat upwardly directed at 

 two distal points which more or less distinctly give it the 

 form of a trifoliate or ogee arch. The space above the shelf 

 is, however, to a considerable extent due to the fact that this 

 part of the zocecium overlaps the next zooecium on its distal 

 side, the curved transverse line (fig. .11 «) being the upper 

 end of the wall of separation between the cavity of the b 

 zooecium and that of its next neighbour distally. The oral 

 arch is not much raised ; it is rounded in A zooecia, quad- 

 rangular (with rounded distal corners) and parallel-sided in B. 

 The cryptocyst is thin, with large pores; it slopes gradually 

 and gently into the median process and the lateral recesses, 

 its slope often beginning from its proximal border, so that it 

 is hardly possible to speak of a horizontal portion as in most 

 of the species. From the cryptocyst which enters the median 

 process the upper wall of the tube usually rises without any 

 angulation. The descending part of the cryptocyst is, owing 

 to its slight descent, much more easily seen than in any of 

 the preceding species, and it entirely hides the basal wall of 

 the zocecium, except by deep focussing through the opening 



