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flat or gently concave, its plane being placed in such a waj' as to project most on the median 

 side, and falling away towards the outer side of the branch. This flat surface is bordered by 

 a longitudinal ridge on each side; and these ridges are recognizable as longitudinal ridges 

 some way down the branch. A few pores occur on the flat surfaces. In the older branches 

 (fig. 1 2) a considerable amount of thickening is found to have taken place. The middle line 

 of the branch is the most projecting part; but the ridges have become less regular and more 

 numerous, and are wider than at first, with evenly roundecl summits. Pores are visible in the 

 intervals between the ridges, and the external opening of the pore is commonly longitudinally 

 slit-like. A few sharp spines are developed, here and there, on the frontal surfaces of the 

 zooecia, principally on the ridges. On the basal surface the spines may be numerous, but are 

 shorter and conical. 



The greatest development of the spines occurs, hovvever, on the peristomes, both of 

 the inner and of the outer zooecia. They may be regard ed as due partly to the splitting of 

 the peristome, at its free end, into a certain number of sharp spines, of which two on the 

 distal border and a stronger, median, suboral spine are usually the largest (fig. 10). The 

 peristome bears other spines, as well as these, and some of them radiate into the orifice, as 

 has been pointed out by Kirkpatrick. 



The shape of the outer peristomes is variable. In some cases (fig. 9) the peristome 

 does not widen at its distal end, and the spines are more or less equally developed all round, 

 although even in these zooecia the suboral spine is generally distinguishable. 112. B. included 

 two specimens, of very different appearance. In one of these (fig. 1 2) most of the outer 

 peristomes widen considerably at their distal end, where there is a marked calcareous collar 

 round most of the orifice, being specially developed proximally and laterally. The suboral 

 spine is produced from the middle line of this collar, and may be strengthened by a longitudinal 

 buttress running down the frontal surface of the zooecium. The collar forms a concave shelf- 

 like surface, starting from the inner aspect of the suboral spine and passing to the sides of 

 the orifice. In the other specimen (figs 8, 10) from the same dredging the peristomes of 

 the outer zooecia are greatly compressed ; and they are further remarkable for the enormous 

 development of the suboral spine, which is compressed and finely denticulate, and may be as 

 long as the peristome itself. A similar suboral spine may be found on the inner zooecia as well. 



In the basal view of young zooecia (fig. 11) a strong longitudinal ridge is generally 

 discernible along each edge of this surface. Where the two distal spines are large, one of these 

 ridges is seen to pass into each spine; and the ridges themselves may be plate-like and very 

 high, so that each lateral border of the basal surface bears a high flange. The basal ridges of 

 the terminal zooecium of the branch can be traced into the two ridges which run longitudinally 

 along the back of the young branch (fig. 11). These ridges become joined by others which 

 belong to the more proximally situated zooecia, and the number is thus increased. In the older 

 branches the basal ridges are not so regularly longitudinal and they have a more rounded 

 surface, between them occurring the pores, each of which generally lies in a somewhat lozenge- 

 shaped depression (upper part of fig. 11), of the kind so frequently seen in species of Hornera. 

 The outer ends of the pores are generally longitudinally slit-like. 



14S 



