274 SIDNEY F. HAHMEi;. 



like a narrow border on each side of the opening. Tlie a 

 opercula of this specimen are perfectly typical, and two b 

 opercula found, so far as can be seen in the dry preparation, 

 are in no way remarkable. The specimen has much less than 

 the normal proportion of b zooecia. 



The South African specimens (a, h) show the simple cha- 

 racter of the cryptocyst in a somewhat less marked way. 

 The sides of the median process are usually continued 

 obliquely across the proximal border of the lateral recesses 

 as far as the sides of the zooecia, though fading away to a 

 mere line before they reach this part. The lateral recesses 

 are thus sharply outlined; their floor is at a hardly deeper 

 level than that of the cavity of the median process, and its 

 plane is somewhat different, since it slopes basalwards as it 

 passes from the tube to the side of the zooecium. In a few 

 cases a distinct curved line, with its concavity towards the 

 median process, runs transversely across the cryptocyst from 

 one lateral recess to the other. The part of the cryptocyst on 

 the distal side of this line is thin-walled, transparent, and 

 usually without pores. I can oifer no suggestion Avith regard 

 to this appearance, which may have bearings on the function 

 of the median process. The difference in the size of the 

 lateral recesses in a and b is striking, indicating a diffei'ence 

 in the development of their muscular system. The opening 

 of the tube is usually narrower distally ; its sides meet the 

 distal wall in a highly characteristic way ; they are alike in 

 both A and b, and the first impression produced by examining 

 them without sufficient focussing is that of a line on each side 

 of the opening fixed to the distal wall by an expanded foot. 

 The lateral wall of the tube is, in fact, somewhat expanded 

 and thickened Avhere it joins the distal wall. The tentacle- 

 sheath, in its passage through the tube, must lie in contact 

 with the distal wall, instead of being separated from it, as in 

 some other species, by a part of the cryptocyst. The basal 

 wall of the zocEcium is not visible from above, except by deep 

 focussing through the opening of the tube. The back shows 

 merely the origin of the four vertical walls. The proximal 



