Ascodictyon and Ehopalonaria, 



85 



upon their origin and development. In fig. IV. I Lave given 

 sketches of four distinct types of very common forms fomid in 

 the shales. In fig. IV. 1 we have the rarest of these, showing 

 elongated cells very similar to some of the cells of Stomato- 

 pora elongata, Vine (fig. IV. 2), only that the cells are in an 

 opposite direction to what (apparently?) is the case in >S'. 

 elongata. I cannot, however, detect any orifices in these cells 

 such as we have in 8. elongata. 



Another form, very common indeed, is shown in fig. IV. e3. 

 Only that the cells are not club-shaped, I suggested for this 

 type R. boteUus, as descriptive of its peculiar sausage-like 

 character. But even of this type better evidence is afforded by 



Fi^. IV. 



6^- 



1, 3, 4, 5, RJiopalonaria, ITlricli : species described in text, 

 2. Stomatopora elongata, Vine. 



fig. IV. 4, in which both the boielloid and the rhopahid charac- 

 ters are shown in one colony. Some of the cells in the last figure 

 liave, one would suppose at first sight, cell-mouths. This is 

 not so : those cells that are shown thus are a little more cal- 

 careous than the others ; the walls are broken at this part, 

 and the dark brown matter is shown below. I have some 

 few specimens of the last two types, and the whole of the 

 walls or outer covering is destroyed, and the hotella-V\ke 

 matrix is still adherent to the fragments to which the original 

 organism was fixed. In fig. IV. 5 we have a fourth and 



