BY E. F. HALLMANN. 



481 



lation; on close inspection, it presents a minutely reticulate ap- 

 pearance due to tlie dermal pores (PI. xxvi., fig.4). The dermal 

 membrane is thin and (owing to the multitude and close apposi- 

 tion of the minute pores) of gauzy appearance,— permitting to 

 be perceived through it, more or less distinctly, the subdermal 

 pinhole-like openings which are the entrances of the incurrent 

 canals. The consistency is rather fleshy, soft, and resilient, and 

 the branches ai-e flexible and lax. The colour in alcohol is pale 

 orange-yellow. 



'I'he dermal pores are arranged in closely approximated, oval 

 to circular groups or "pore-sieves" (PI. xxvi., figs. 4, 7; PI. xxvii., 

 fig 5) containing each from 3 to 8 pores, and measuring up to 

 350/i in diameter; the pores themselves measure from 50 to about 

 lOOji in diameter. Very commonly, the boundaries between the 

 sieves are scarcely more pionounced or wider than those sepa- 

 rating the pores, so that, in places, the lines of demarcation 

 between the sieves become obscure and the pores appear almost 

 to be uniformly distributed. Witliin the pore-sieves, the dermal 

 membrane is extremely thin, and contains but very few spirulae 

 sparsely scattered. 



Skeleton. The skeletal axis or core is much more sliarply de- 

 fined and delimited tlian in any other of the species, and is 

 equalled in density only liy that of T. fastiyatus; in comparison 

 with the stoutness of the branches, it is rather slender, measur- 

 ing in diameter generally not more than two-thirds of the length 

 of the radial fibres. The radial fibres proceed outwards from the 

 axis in a direction inclined to it at an angle of 60° and upwards, 

 and arrive at the surface almost perpendicularly thereto. Con- 

 necting fibres between the radial tibres are extremely few; con- 

 sequently, in the prepared or macerated skeleton (PI xxiii. fig.5), 

 the radial fibres are easily disarranged and thus usually present 

 a somewhat dishevelled appearance. The colour of the skeleton 

 is pearl-grey except axially, where it is brownish-grey. The 

 i-adial fibres are rarely as much as oO/^t in stoutness, and are 

 usually provided with a distinct layer of spongin external to the 

 spicules. The connecting fibres consist frequently of only a 

 single spicule, and .seldom of more than two, 



39 



ij L I s?J R A K 



