262 



The ooecia are in all essentials of a similar form and structure as in the 

 preceding species; but the two free, rib-like processes are not bent like a hook. 



The colonies are richly branched, bifurcated and with the zooecia arranged 

 in two rows, which have their apertures turned in an opposite direction. 



Colonies from Victoria. 



Calwellia bicornis W. Thomps. ' 

 (PI. XIII, figs. 8 a— 8 c). 



The zooecia are opposite, disposed in pairs and in such a waj' that the di- 

 rection of each pair is vertical to that of the preceding or succeeding pair. 

 While the distal terminal parts of a pair of zooecia meet with their basal sur- 

 faces, the two corresponding proximal stem-like parts, which are of a triangular 

 transverse section, are on the contrary separated in the whole of their length by 

 the terminal parts of the proximally situated pair of zooecia (fig. 8 c), each of 

 them touching with its inner edge one end of the separating wall, which the two 

 just-mentioned basal surfaces share in common. No rosette-plates are found in 

 this wall, but there is a multiporous rosette-plate - (fig. 8 a) in the distal end of 

 each stem-like part on each of the two surfaces which are bent towards each 

 other at an angle, and an inner communication is thus brought about between 

 the stem-like part of the distally situated pair of zooecia and the distal end of 

 the proximally situated pair. Each stem-like part ends proximally in a small, 

 sharply defined, rounded portion, and proximally to it is seen the narrow, angul- 

 arly bent distal wall (figs. 8 a, 8 b) which is furnished with a multiporous ro- 

 sette-plate centrally. The strongly arched distal portion of the zooecia, which 

 greatly increases in breadth from its very narrow proximal part towards the dis- 

 tal end, is on either side of the apertur^ provided with a short, robust spine, 

 which is rounded at the end. The transversely oval aperture has a compound 

 operculum. A sutural line connects it with the transversely oval crescentic asco- 

 pore, which has a slight distal concavity. On the proximal as well as on the 

 distal side of the aperture we find two widely separated, transversely oval, uni- 

 porous rosette-plates. 



Ooecia are wanting in the examined colonies; but Wyv. Thompson's figure 

 shows that they are provided with finely, transversely striated ridges disposed in 

 the shape of a fan. They are present in some colonies of C. gracilis Maples, ori- 

 ginating from Bass' Strait, which species differs from C. bicornis for one thing in 

 having a simple operculum with a straight proximal margin. In this species also 



104, 1). 92. PI, IX, figs. 2, 2 a 



