74 Mr. li. Kiikpatrick on the 



ooecia are half immersed in the superjacent zooecium, cucul- 

 late, rather flattened from befoie backwards ; marked with a 

 short vertical ridge bifurcating- above, and by a horizontal 

 ridge formed by the lower border of the zooecium above. 



Family Membraniporidae. 



Genus Membeanipora. 



Meriibranipora d<fenso, n. sp. (PI. VI J I. fig. 8.) 

 Zooecia corneous, large, ovate, slightly produced below ; 

 aperture oval, witli raised, slightly crenulated margin ; one 

 short, thick, upright, bifurcate, oral spine at each upper 

 angle, and 6-8 flattened spines on each side, bending over 

 the aperture, interdigitating. No avicularia. Ooecia ? 



In some instances the spines have fused, thus forming- 

 solid bars above the aperture, and foreshadowing what takes 

 place more completely in 3IemhraniporeIla. 



Ilemhranipora onarginalis, n. sp. (PI. VII. fig. 2.) 



Zoarium incrusting. Zooecia large, oval, slightly produced 

 below the area, the produced portion being thick, hyaline, 

 marked with concentric curved lines ; area oval, wider below 

 than above ; margin thick, sloping inwards to aperture, 

 slightly crenate ; no internal calcareous lamina ; no avicu- 

 laria. Ooecia cucuUate, smooth. 



MemhraniiJora maiiritimia^ n. sp. (PI. VII. fig. 3.) 



Zoarium incrusting. Zooecia varying in shape, generally 

 oval ; separated from each other by short tubes ; very slightly 

 produced below the area ; walls of zooecia hyaline in younger, 

 opaque in older cells, granulose ; area surrounded by a high 

 crenulated border, oval, wider below than above j lamina 

 hyaline, granulose ; aperture (portion uncovered by encroach- 

 ment of lamina) shaped like a wide figure of eight ; orifice of 

 zooecium at top of cell semicircular, not truly articulated. 

 Ooecium cucullate, smooth, opaque, not punctured. 



'Ihe inter-zcoecial tubes are hardly discernible in the older 

 parts of the colony ; also the portions of the zooecia produced 

 below the area are obliterated. 



Whether those forms of the Membraniporidaj with a cal- 

 careous lamina partially covering the " area " should be 

 included under a distinct genus (viz. Amphiblestrum) or not 

 is a vexed question. 



The forms with the lamina seem to be intermediate betvv een 

 Memhranipora proper and Microiwra^ the latter geims being 



