676 E. KIRKPATRIOK. 



zontal tabular and vertical (or columnar) sutures were 

 beautifully lighted up. 



Tlie disposition of these vertical and horizontal sutures 

 clearly shows how the skeleton has been built up. The 

 structural unit is a broadly based pillar with three vertical 

 lougitudiual wings or flanges (which unite with the flanges of 

 three juxtaposed columns), and with three vertical longi- 

 tudinal curved surfaces or flutiugs which form a part or 

 segment oF the walls of three tubes, and lastly with tieis 

 usually of three horizontal triangular tabular segments in one 

 plane, the number ot" tiers varying with the number of tabula?, 

 (See diagrams a, b, c in text.) 



It was a surprise to find that there was no continuous 

 floor such as was depicted (in vertical section) in my oiiginnl 

 figure. (7) The seeming existence of a floor in certain places 

 is apparently due to tlie section cutting through the thick 

 outspread base of a vertical wall. 



It is certain there is no coniinuous basal lamina at the 

 periphery of thin spreading crusts, but occasionally I 

 have seen what appear to be complete floors at the base of 

 some of the basal crypts. The floor of Merlia is formed by 

 the shells, coralline algae, Foraminifera, etc., ou which the 

 sponge is growing. The vertical walls of the lowest crypts, 

 (_)ften tliickened and spread out a little at their bases, are 

 intimately fused with the foreign foundation. 



Under a fairly high power the skeleton shows a finely 

 fibrillar structure (PI. 35, figs. 16, 17). When the skeleton is 

 viewed from the surface, the fibrillas are seen to radiate out 

 fpDUi below the base of each tubercle towards the longitudinal 

 sutures, where they meet but do not blend with the fibrilhie 

 of opposite flanges (PI. 35, fig. 16). Superposed zones of 

 fan-like bands of striae radiate upwards and outwards from 

 the vertical axes of the columns of the skeleton and pass into 

 tlie tabuhe and walls of the tubes (PI. 35, fig. 17). 



An English colleague was engaged, iit the time this was 

 being written, in the attempt to show that Merlia was a 

 Foraminiferan. He had only a dried skeleton, coming, I 



