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obliquely distally and outwards, project freely from the surface of the zooecium, 

 but in the older zocecia they become more or less deeply sunken owing to the 

 above-mentioned deposition of calcareous layers. At their base we find as a rule 

 two of the above-mentioned, original calcareous ribs, which from their position 

 have not been able to share in the increase in thickness like the others. 



Of this species I have examined some small, dry colonies from Foveaux 

 Straits, N. Zealand (Dr. Harmer). 



Porella (?) cornuta n. sp. 

 (PI. XVIII, figs. 6 a-b, PI. XXII, fig. 11 a). 



The zooecia elongated, quadrangular or hexagonal, fairly strongly arched, 

 with closely placed, scattered, large, round or oval pores, between which are 

 numerous small tubercles. The half-elliptic aperture is provided with a very broad 

 but extremely low sinus, which has a straight or slightly convex, proximal margin 

 and is marked off on each side from the lateral margins by a small, rounded, 

 tooth-like projection Immediately distally to and inside this projection, there is 

 on each side a rounded, triangular hinge-tooth, which is continued into a weakly 

 developed vestibular arch. In the distal part of the aperture the peristome is 

 only weakly developed, but in its proximal half there is on each side a collar- 

 shaped, prominent, fairly thick projection, which on each side grades into the 

 avicularium and in the ooecium-bearing zooecia meets the proximal part of the 

 ocecium, whilst in the other zooecia it is sharply marked off from the low distal 

 part of the peristome. The operculum (PI. XXII, fig. 11 a), which has a similar 

 form as the aperture, is only slightly chitinized but distinctly separated from the 

 compensation-sac. On each side within the margin it has an elongated, strong 

 ridge and the two ridges pass over both distally and proximally into a somewhat 

 strongly chitinized, but not very distinct, connecting part. Each distal wall is 

 provided with two and the distal half of each lateral wall with one multiporous 

 rosette-plate. 



The ooecia are as a rule elongated, more or less distinctly tapering upwards, 

 strongly arched and with their frontal wall inclined down towards the aperture. 

 They are in the beginning furnished with fine radiating striae, but owing to later 

 calcification this striation becomes more and more indistinct, and the older ooe- 

 cia are not only provided with smaller and larger tubercles and with rib-like 

 prominences of varying form, but most of them have even one or several, shorter 

 or longer, sometimes very long, hollow spine-like processes of more or less reg- 

 ular form. There is often such a process standing out almost perpendicularly 

 from the surface of the ocecium in the neighbourhood of the aperture on both 



