149 



with a strongly chitinized margin. The lateral margins of the operculum form 

 right angles with the distal margin. The distal wall has within its basal edge a 

 transverse row of 3—5 small uniporous rosette-plates, while the distal half of 

 each lateral wall has 2 multiporous ones. 



The colonies examined form incrustings on Amansia pinnatifida from Austra- 

 lia. (The herbarium of algae in the Botanical Museum). This species is most 

 closely allied to Membranipora nitens Hincks, which must also be referred to the 

 genus Electra and shows more distinct signs of the relationship than E. bicolor. 

 It has as in E. pilosa an obliquely ascending distal wall, and the three promi- 

 nent spines, so often occurring within the genus, viz. the unpaired proximal and 

 the two distal, are here represented, the former by the large conical expansion 

 and the latter by two somewhat compressed tubercles, which are connected by 

 an arch-like ridge. The rosette-plates are of the same structure as in E. bicolor. 



E. angulata n. sp. 



(PI. XXII, fig. 4 a). 



The zooecia of varying form and dimensions, with a distal arch-like or 

 angulate margin and with a large, most often oval, membranous frontal area, 

 occupying the greater part of the frontal surface. There is a slightly developed, 

 granular, dentate, secondary cryptocyst. In respect to development of spines the 

 zooecia show great differences. The best provided ones, which in the colonies 

 examined are in a great minority, have on the margin 12 not very thick spines, 

 which reach the middle of the area or even surpass it. A larger or smaller 

 number of them is however often wanting, and many zooecia are altogether 

 without spines. On the proximal gymnocyst we find in most zooecia 2 (more 

 rarely a single median and still more seldom 3) short, thick, conical spines, 

 generally open at the end, which are situated half-way between the central line 

 and the lateral margins. These spines may sometimes be rudimentary, and in 

 many zooecia (with or without marginal spines) they are absent. The distal wall, 

 which is generally ascending towards the frontal surface and angularly bent 

 from side to side or arch-like, has on either side a rather large, multiporous 

 rosette-plate situated in one of the basal corners of the distal wall. The distal 

 half of each lateral wall has a single multiporous rosette-plate. 



On a ligneous core taken on the surface of the water near Koh Samit, Siam 

 (Dr. Th. Mortensen). 



In a variety of this, species from lat. 22" 10' V. long., 114" 30' E. (Captain 

 Suensson) the separate zooecia attain considerably larger dimensions and are in 

 the examined colony all provided with 20 — 24 marginal, spines and with 1 — 3 



