A REVISION OF THE GKNUS STKGANOFOKELLA. 263 



structure. The periphery of the median process is everted. 

 The cavity of the process, when seen from the distal side 

 (fig. 30), is thus like a ilask with a narrow neck and a spread- 

 ing mouth. The tube (t.) is little more than a circular open- 

 ing in the vertical cryptocyst. The opening is large, and 

 commonly of the same width as the zooecium itself at this 

 level. While it is usually separated from the deepest point 

 of the zooecium by a part of the cryptocyst, its lateral 

 boundaries are formed by the lateral Avails of the zooecium, 

 an arrangement peculiar to this form. In some cases the 

 tube may, however, occupy the entire deeper part of the 

 zooecium. Each lateral wing of the median process commonly 

 comes into contact with a tooth given off from the lateral part 

 of the zooecium, thus limiting a complete '' opesiule " (fig. 4). 

 The lateral recesses (fig. 30, /. r.) have an unusual form. 

 They are completely vertical, and, sharing in the great depth 

 of the median process, they take the form of cavities which 

 appear triangular when seen from the distal side, their apices 

 being directed towards the axis of the branch. 



The epithecal sclerites (fig. 4, e.s.) are rather short, and 

 do not quite reach the base of the operculum. No b zooecia 

 have been found. The a opercula (fig. 25) liave four well- 

 developed teeth on the main sclerite, which is massive, its 

 proximal ends projecting considerably as rounded, sometimes 

 trifoliate lobes. The area included within the semicircular 

 main sclerite is occupied by a complicated system of smaller 

 secondary sclerites. A varying number of longitudinal bais, 

 usually converging towai-ds the middle line, and uniting with 

 one another in various ways, start from a basal sclerite, and 

 are united by a more or less transverse sclerite, which joins 

 the main sclerite at its two ends, and may give off distally 

 irregular longitudinal sclerites, some of which may join the 

 main sclerite. This set of sclerites is highly variable. Each 

 is a girder-like thickening, like the other sclerites of the 

 operculum. 



The size of the opercula is very constant, averaging about 

 450 fi. That of the specimen drawn is 500 ^, 



VOL. 43, PART 2. NEW SERIES, T 



