244 SIDNEY F. HARMER. 



longitudinal row of zooecia. If tlie series bifurcates^ the 

 two daugliter-zooecia may have the same asymmetry as their 

 parent, or oue of them may have the converse symmetry; or 

 both may be converse. I suspect that the asymmetry is cor- 

 related with the position of tlie retracted polypide, and that 

 the tentacles lie in some zooecia on the right side, and in the 

 others on the left side. In the specimen figured the tube 

 springs from the (apparent) right side of the subopercular 

 cavity. The proximal wall of the right ^ lateral recess is not 

 apparent in the figure, while that of the left recess is just 

 visible. Between this wall of the left lateral recess and the 

 tube the basal wall is exposed to view from above. On 

 turning the zooecium over this appears as a deep sinus (fig. 

 27) passing proximally and asymmetrically in correlation 

 with the asymmetry of the tube itself. A view from this 

 side at once shows that there is considerable variation in 

 these respects. The condition shown in the upper zocecium 

 of fig. 27 corresponds with that of fig. 1 ; that shown in the 

 lower zocBcium indicates that the cryptocyst does not any- 

 where touch the distal wall, while another condition is 

 found when the cryptocystal floor of the lateral recess 

 meets the distal wall (in any case very low down) on both 

 sides. 



The upper border of the opening of the tube is produced 

 into two points, which are typically asymmetrical, that on 

 the side of the sinus being more developed than the other, 

 as indicated by fig. 1. The edge (see p. 227) of the zooecium 

 is hardly as high as the calcareous post-oral shelf, from 

 which it is separated by a distinct furrow. The shelf is 

 strongly tubercular, but is not so deep as in most species. 

 The horizontal part of the cryptocyst is accordingly com- 

 paratively little depressed below the level of the epitheca ; 

 it is well developed, thick, and tubercular, and has small 

 pores. A strong tubercular continuation of the shelf runs 



• It will be convenient to describe what is actually seen in the figures, 

 without alluding on each occasion to the fact that the figure has been re- 

 versed by the microscope. 



