148 



mally to the centre an opercular valve, on the proximal side of which there 

 is a long, strong spine. The two rows of flat spines, which cover the area on 

 the distal side of the valve, generally meet in truncated ends. We may how- 

 ever sometimes, as in the corresponding formation in E. zostericola, see a spine 

 stretching its terminal part across an opposite s\nne. The basal wall is only 

 calcified in the distal, ribbed half of the zoa'cium. A small piece of this species 

 was kindly placed at my disposal by the late Mr. Peal. 



Var. brevispina n. (fig. 1 c). 



The ordinary zooecia are larger, narrower at the base, the frontal area sur- 

 rounded by 8 — 9 short spines, the proximal one but slightly stronger than the 

 others. The dentiform ]n-ocesses are represented by about 10 extremely small 

 tubercles, situated within the margin of the frontal area in the distal half of 

 the latter. 



The orecium-bearing zooecia are larger than in the principal form, have 

 fewer spines and a semi-circle of o short spines proximally to the aperture. 



A few colonies of this form have been found on Honnophora Anstralasiae in 

 the herbarium of alga; in the Botanical Museum. Although we do not under- 

 stand the significance of the situation of the aperture behind the area formed 

 by the spines, we must still group this form of oojcium with the one found in 

 E. zostericola. 



Electra bicolor Hincks. 



Membranipora bicolor Hincks, 



Annals Nat. Hist., ser. 5, Vol. VII, 1881, pag. US. 



(PI. IX, figs. 7a-7c). 



The zooecia very long, narrow (the length larger than the breadlli by about 

 3^2 times), somewhat lyre-shaped, with a longitudinally oval, membranous frontal 

 area, occupying about three-fourths of the whole length of the zooecium and 

 bounded by somewhat convex lateral walls. The smooth, arched gymnocyst 

 passes into a cryptocyst, which first sinks obliquely distally and inwards and 

 finally gives off towards the basal wall of the zooecium a horizontal lamina 

 ending in a denticulated margin (fig. 7 c). On the boundary between the oblique 

 semi-elliptical and the horizontal denticulate part of the cryptocyst a triang- 

 ular calcareous lamina takes its origin. It consists of two lateral halves, bent 

 against each other at an angle open outwardly, and which meet in a 

 thickened central ridge (figs. 7 a, 7 b). In rare cases the gymnocyst has a small 

 tubercle-like expansion distally. The frontal margin of the distal wall is strongly 

 thickened and crenulated, and on the proximal side of it the operculum is seen 



