Anatomy of the Temnopleuridai. 123 



narrow, wavy lines. This ornamentation is also seen upon 

 the main stem or water-tube. 



The hollow of a process is lined with a smaller and less 

 columnar endothelium, with granules, and it appears to line a 

 somewhat irregular basement membrane (fig. 18). Between 

 the outer and inner series of cells is a somewhat wide space 

 readily transmitting light, and having no definite structures 

 in it, and in specimens which have not been decalcified cal- 

 careous spicules are found there in some abundance. 



In Salmacis (fig. 20) the branchiae are larger and stouter 

 than in Temnoiileuras] they are, however, narrow and spring 

 from a larger and higher stem. The processes are more in 

 tufts, and are shorter and more numerous than in Temno- 

 fleuTus. These branchiee pass up over the margin of the 

 peristome at the branchial grooves and reach along the flanks 

 of the ambulacra for a line or two. The principal structure 

 to be noticed is that which is visible before applying acids. 

 The calcareous spicula are separate, moderately nuuierous, 

 and variable in size and shape. " C "-shaped spicula are 

 seen, but are not common, and the others are bifurcate or 

 pinnate ; and on the water-tube there are numerous fenestrated 

 elliptical or irregularly shaped plates. 



The Am;pull(B. (PI. XI. figs. 21, 22.) 



Decalcified portions of the ambulacra of Temnopleurus 

 toreuviaticus stained with heematoxylon were used. The 

 ampullar are small and bolster-shaped near the apical disk 

 and become gradually larger and closer in vertical succession 

 towards the ambitus, where they are large, long, from side to 

 side, and tallest near the median ambulacral water-tube (fig. 

 21). Their actinal edge is tumid and more or less gibbous, 

 a swelling being noticed close to the water-tube and a con- 

 traction midway between the two ends, and there is more or 

 less of a narrowing quite at the part which corresponds to the 

 poriferous zone. The abactinal edge is less irregular and 

 runs up to a blunt point at the poriferous zone end. They 

 are broader than high and tumid. The opening into the 

 water tube is seen by transmitted light very plainly, but the 

 holes for the tentacular canals are indistinct. They are placed 

 in the interradial side half of the ampullee and are recognized 

 as a dull elliptical space, which appears to be more or less 

 occupied by fibres of the inner part of the base of a tentacle 

 whicii have become compressed over the openings of the 

 pores externally. 



The structure of the walls of the ampullaj is very interest- 



