250 



of the zooecium. They attain their greatest extent on the basal surface, on which 

 they are separated partly by a rather broad longitudinal belt, which is some- 

 what concave towards the centre and bifurcated in the bizocecial joint, partly 

 by the belt-shaped or ridge-like lateral branches, likewise concave and springing 

 from the just-mentioned belt. The supra-scapular chamber reaches some way 

 down the basal surface, but a still larger part of it can be seen on the frontal 

 surface, where the two chambers are separated by a narrow ridge passing down 

 to the incision between the two umbellate pi'ocesses of the aperture, the free 

 edges of which form part of the boundary of the two chambers. From the proxi- 

 mal end of each umbel the boundary ridge runs in a straight line towards the 

 avicularium and then bends in an arch-shaped ridge, the distal part of which is 

 parallel with the margin of the frontal area of the avicularium. The infra- 

 scapular chambers, which are the largest, form the greater part of the basal 

 surface of the zooecium and a large part of its lateral surfaces, and each cham- 

 ber is separated from the large, rounded quadrangular pedal chamber (fig. 5 b) 

 by a ridge springing from the proximal end of the basal wall, which first passes 

 obliquely distally and after another bending joins the sternal area. In the bi- 

 zocecial internode the greater part of the distal surface is occupied by a large 

 membranous chamber, which sends a triangular portion down the frontal as well 

 as the basal surface. This chamber is bounded on either side by a low ridge, 

 which runs from the ring of the joint to the incision in the bilobate marginal 

 expansion of the aperture (fig. 5 e). A thick but rather short horizontal ridge, 

 situated immediately on the distal side of the intermediate space between the two 

 apertures (fig. 5 e), incompletely divides the chamber into two parts, viz. a smaller 

 frontal one and a larger distal and basal. Each of these communicates with the 

 daughter-zooecium through a small rosette^plate with 2 — 3 pores, and the entire 

 chamber must be regarded as the adzooecial, supra-scapular chamber of the 

 mother-zooecium. The adzooecial infra-scapular chamber of the mother-zooecium 

 is wanting, and with regard to the other chambers in the bizocecial joint refer- 

 ence may be made to the explanation of the plates. 



The ooecium. The gonozooecium, which is only about half as high as the 

 covering kenozooecium, is situated sometimes on a mother-zooecium, sometimes 

 on an inserted single zooecium. The sternal area, which is a little smaller than 

 the aperture, is provided with 5 elongated fenestrse somewhat pointed at the dis- 

 tal end, which increase in length towards the centre but all reach nearly right 

 up to the proximal margin of the aperture. Inside this row of openings, which 

 reminds one of a visor, a very broad, rounded cryptocyst lamina is seen. On the 

 other hand a frontal sinus and ribs or spines are completely wanting. The 



