146 



Electra Lamour. 



Tendra Nordm. p. p., Pyripora Mc Coy p. p., 



Heterooecium Hincks. 



The frontal calcification of the zooecia is essentially or exclusively a gymno- 

 cyst. There may be a circle of spines round the frontal area, of which an un- 

 paired proximal one is generally the most constant and often the only one pre- 

 sent. The distal wall is furnished within its proximal margin with a transverse 

 row or a transverse belt of uniporous rosette-plates; the lateral walls have 2 — 3 

 multiporous plates. No avicularia. Ooecia absent or acanthostegous. 



To this genus I refer E. verticillata, E. pilosa, E. bellula, E. triacantha, E. 

 distorta, E. zostericola, E. amplectens, E. monostachys, E. fossaria and E. catenu- 

 laria which like E. fossaria has a calcified operculum and can only be regarded 

 as a form of the latter. I have some doubt whether the species, which has 

 hitherto wronglj"^ been called M. Lacroixi, and for which I propose the name of 

 M. hippopus, can be referred to this genus. 



E. zostericola Nordmann. 

 Tendra zostericola RepiachofF, Zeitschrift fiir wissensch. Zoologie, 25. B., 1875, 



pag. 129, Tab. 7—9. 

 Membranipora (Tendra) zostericola Ostroumoff, Die Bryozoen der Bucht von 

 Sebastopdl, pag. 18, Tab. 1, Fig. 13—14. 

 (PI. IX, figs. 2 a-2 b). 

 As shown by the above-mentioned authors there is among the ordinary zooecia, 

 which have generally only two distal and sometimes one proximal, unpaired 

 spine, a smaller number, in which as in ^e Membraniporella species the mem- 

 branous frontal area is covered by two rows (10 — 17 pair) of hollow, very thin- 

 walled spines, which meet in the central line of the zocecium. Their form is 

 extremely variable in the same zocecium, as they are sometimes broad, some- 

 times narrow, sometimes single, sometimes bifurcate in a larger or smaller part 

 of their length. Two opposite spines most often meet in a truncated terminal 

 part, but it is not infrequent, that a greater or smaller number of them stretch 

 a thin point across the end of an opposite spine. The bright spots seen at the 

 outer part of each row are the translucent cavities of the separate spines. Of 

 these the distal ones are the shortest, and the gymnocyst projecting here into a 

 triangular portion, which has a curved margin distally, leaves a small trans- 

 versely oval area for the opercular valve. The two rows of spines form a some- 

 what arched roof across the frontal membrane, and thus a space is formed which 



