208 PROCEEDINGS OF THE 



the fronds of the fenestrated species should be found, in almost 

 every instance, with the celluliferous face adherent to the stone in 

 which they are embedded. The reason for the fronds being so 

 persistently adherent by this face, is that the pores on the celluli- 

 ferous face have often raised margins, and are more or less slightly 

 projecting beyond the surface of the frond, giving it a rougher 

 aspect, while the non-celluliferous face is comparatively smooth, 

 being only faintly striated or granulated in most instances. This 

 smoother face is consequently much less adherent to the matrix 

 than the celluliferous face, and is therefore that which is most 

 constantly exposed. In some of the harder limestone shales, such 

 as those of Hairmyres, East Kilbride, and of the Beith and Dairy 

 districts in Ayrshire, we sometimes find the fronds of the Polyzoa 

 showing the celluliferous face, but this is owing to the circumstance 

 that there the fronds have been fixed down by one or other face 

 upon a layer of harder shale or limestone, and have been covered 

 by a layer of softer shale, so that when the rock comes to be split 

 up, the parting is in the line of the soft shale; so those specimens 

 that chance to have their celluliferous faces next to the soft layer 

 are now and again exposed. On the other hand, where the 

 Polyzoa are embedded in soft shales that yield readily to the 

 influence of the weather, like those of Dikehead, High Blantyre, 

 or Gillfoot, Carluke, the tendency in them is for the celluliferous 

 face to adhere to the matrix. However beautiful fronds of 

 Polyzoa showing only the reverse face may be, they are much 

 more beautiful, and become more valuable to palaeontologists as 

 specimens, when the celluliferous face can be examined, for it is 

 only by the number and form of the cells in the fenestrules that the 

 several species belonging to the various fenestrated genera can be 

 correctly determined. 



Recently Dr Eankin of Carluke, when examining the Polyzoa 

 of the Gillfoot shale, was led to try the experiment of fixing small 

 portions of the fronds of Polyzoa by their non-celluliferous face to 

 a bit of melted black sealing-wax, which adhered firmly to the 

 frond. On the shale being placed in water, the wax brought away 

 the bit of Polyzoa w4th its celluliferous face exposed, which on 

 being cleaned, by washing with a brush in w\ater, allowed the cells 

 to be clearly examined. To Dr Rankin, therefore, am I indebted 

 for the hint that first led me to try the same experiment on large 

 fronds of Polyzoa, but using instead of the black sealing-wax, a 



