472 REVISIOK OF THE AXIKELLID^, i., 



Abnormal forms among the microstrongyla (of the kind shown 

 in the Text-fig.) are of more frequent occurrence in the present, 

 than in any other of the species excepting T. pustulosus, their 

 proportionate number being not less than one in thirty. 



Trachycladus digitatus var. gracilis, var.nov. 

 (PL xxii., fig.3; PI. xxiii., fig.2; PI. xxvii., fig.2.) 



Didynoais. — Branches slender (2 to 3"5mni. in diameter); of 

 uniform diameter throughout their length. Oscula scattered 

 irregularly. Dermal layer with closely packed spirula- through- 

 out its entire thickness. Radial fibres of lesser length than the 

 diameter of the axial fune. Megascleres almost exclusively 

 sharp-pointed oxea; stylote modifications much more frequent in 

 occurrence than strongylote; maximum size, 530 x 23/x in the 

 stalk, rarely as much as 430 x 15// in the branches. 



Loc. — Port Jackson. 



Occurring in the collection is a single specimen (labelled as 

 from Port Jackson, and well-preserved in alcohol) which, while 

 presenting the more essential features displayed by the typical 

 form of the species, yet differs in many respects so appreciably 

 from the above-described specimens that it seems advisable, pi'o- 

 visionally at least, to regaid it as constituting a separate variety. 

 The differences which distinguish it externally (PI. xxii., fig.3) 

 are chiefly these : the cylindrical, untapered branches are com- 

 paratively slender, measuring only from 2 to 3'5mm. in diameter 

 (the specimen itself being 115 mm. in total height); the con- 

 sistency is very firm, the branches being stifHy flexible and but 

 slightly compressible; and the colour superficially is a subtrans 

 lucent slaty-grey. The size and distribution of the pores and of 

 the oscula are much the same as in the typical variety, except 

 that the pores are smaller (not exceeding iShp. in diameter), and 

 their linear reticulate arrangement (PI. xxvii., fig.2) is more pro- 

 nounced. As in the typical variety also, the main exhalant 

 canals leading to the oscula are visible through the dermal mem- 

 brane, presenting an appearance as of veins; but they are here very 

 • much more distinct, and are traceable for a much greater distance 



