242 SIDNEY F. HARMKR. 



distally descending to join the basal or distal wall of the 

 zooecium. The descending part of the cryptocyst is per- 

 forated by a passage or tube, through which the tentacle- 

 sheath passes to the orifice^ the walls of this passage being 

 developed at least above. The parts of the cavity on either 

 side of the tube form more or less deep lateral recesses, which 

 contain the opercular muscles and those which depress the 

 epitheca. The tube is usually produced into distal and lateral 

 flanges which limit a hollow, the cavity of the median process^ 

 which opens upwards into the space beneath the epitheca. 

 Avicularia of the ordinary type and external ovicells wanting. 



In arranging the species of Steganoporella somewhat 

 different results would be arrived at according to whether 

 the characters of the opercula or of the cryptocyst and of 

 the tube are taken as the basis of the arrangement. The 

 possible affinities of the species may perhaps be indicated by 

 taking three main divisions, as follows : 



(i) B opercula, if present, with a fl-shaped thickening bar 

 or main sclerite ;^ A opex'cula undifferentiated or with two 

 teeth on the main sclerite. 



(ii) B zooecia apparently wanting; a opercula with four 

 teeth on the main sclerite. 



(iii) B opercula with a A-shaped main sclei'ite. 



The cryptocyst usually joins the basal wall in sections (i) 

 and (ii), while it joins the distal wall in most of the species 

 included in section (iii). 



(i) B Opercula, if present, with a fl-shaped main 

 sclerite; a Opercula undifferentiated, or with 

 two teeth on the main sclerite. 



1. Steganoporella lateralis, MacGill. Figs. 1, 19, 20, 27. 



S. lateralis, MacGill., Mon. Tertiary Polyzoa Victoria, 

 •'Trans. Roy. Soc. Victoria,^ iv, 1895, p. 53, pi. vi, fig. 18. 



Cryptocyst joining the basal wall, angulated and thickened 



' The term " sclerite " may coiivenieutly be used for any definite tliickeu- 



