278 MR. H. B. BRADY ON SACCAMMINA CARTERI. 



discover any corresponding post and no Saccammina, but this is 

 only negative evidence. 



"Just below Garrigill Gate I examined the same limestone 

 again, and again noticed the fossil, but in a position from which 

 I could not obtain specimens. It is beautifully seen in this last 

 place, but is not so thickly set as in the others. The specimens 

 on the weathered surface in many cases have lost their arena- 

 ceous tests and appear as quartz beads. 



" I have as yet found no evidence of Saccammina in the upper 

 posts, though I have carefully examined three complete sections 

 of the four-fathom limestone ; indeed, except a few somewhat 

 doubtful specimens from the upper part of the lowest post, its 

 occurrence here seems to be limited to the thin bed I have de- 

 scribed." 



This information is most interesting, and tends to define 

 Saccammina Carteri as peculiar to the lower portion of the 

 four-fathom limestone. 



EXPLANATION OF PLATE XL 



Fig. 1. A piece of Saccammina-timestone from Elf hills, natural size. The 

 upper portion of the figure shows a weathered surface, the lower 

 a fresh fracture. The white spots on the latter indicate the tufts 

 of crystals which often occupy the interior of the chambers. 



Fig. 2. Polythalamous specimens of Saccammina Carteri, natural size. 



Figs. 3 & 4. Broken specimens showing the occasional labyrinthic struc- 

 ture of the inner surface of the test and the crystalline calcareous 

 masses occupying the interior. Fig. 3 magnified 10 diams., fig. 

 4 magnified 15 diams. 



Fig. 5. Transparent section of a segment, infiltrated partially with carbo- 

 nate of lime, partially with silica : a is a lobe of colloid silica. 

 Magnified 29 diams. 



Fig. 6. A portion of the last specimen, at a, more highly magnified, show- 

 ing the structure of the infiltrated test in transverse section. 

 Magnified 80 diams. 



