RESULTS OP DEEP-SEA INVESTIGATIONS — MAPLESTONE. 269 



irregularly elliptical, with a sinus in the lower lip ; peristome 

 thickened unequally, causing the aperture to be irregular in 

 shape. Four to six very small oval avicularia arranged round 

 the thyrostome and occasionally one on the thickened peristome. 

 Base of zoarium nearly flat, with scattered avicularia, some 

 similar to those on the front of the zooecia, others with an acute 

 mandible similar to those on B. biarmata. No indication of the 

 position of the zooecia. 



BlPORA iMAGNIARMATA, Sp.nOV. 



(Plate Ixxv., figs. 3a, 3b.) 



Zoarium conical, 4 mm. high ; 3 mm. broad at base. Zooecia 

 immersed, in slightly slanting vertical series. Thyrostome ellip- 

 tical ; peristomes oval, very much thickened and raised ; a ligu- 

 late operculum with a longitudinal fold ; no indication of a sinus 

 on the lower lip, probably hidden by the operculum. One large 

 acute avicularium (sometimes two) opposite the thyrostomes in 

 the hollow between the series of zooecia, pointing diagonally. 

 Base of zoarium flat, with radial ridges indicating the position 

 of the last series of zooecia and with scattered avicularia, some 

 with round and some with acute mandibles. 



Obs. — These three species are very similar in character. 

 B. biarmata and B. multiarmata are so much alike that it requires 

 a microscope to distinguish them. The principal difference in 

 them is the size and number of avicularia on the surface of the 

 zooecia ; in B. biarmata there is one avicularium on each side of 

 the thyrostomes with long acute mandibles pointing horizontally 

 outwards ; in B. multiarmata there are from four to six very 

 small broadly oval avicularia ranged round the thyrostome. In 

 both these species there is no indication of the position of the 

 last series of zooecia. B. magniarmata is a slightly larger form, 

 the apical angle is greater, there is a single series (sometimes 

 two) of large avicularia between the rows of zooecia, and on the 

 base there is a slight indication of the position of the last series 

 of zooecia. 



BlPORA AMPULLA, Sf. HOV. 



(Plate Ixxvi., figs. 4a, 4b, 5a and 5b.) 



Zoarium disc-shaped hut convex on the upper surface ; 6 to 7 

 mm. in diameter ; calcification covering the whole of the central 

 portion of the upper surface, with a few small round avicularia 

 and pores scattered about. Zooecia flask-shaped and with greatly 

 extended tubular peristomes, which can be seen from above pro- 

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