80 Proceedings of the Royal Physical Society. 



fectly normal. It should also be observed that the diameter 

 of the tube decreases towards the apex, which measures only 

 three centimetres across. In the ordinary form we found that 

 the greatest transverse diameter was at the upper extremity. 



I was at first inclined to consider this specimen a ramose 

 varietal type of E. aspergillum, but, after an examination of 

 it, have come to the conclusion that it is to be regarded as an 

 abnormality. The sponge, while yet in a very young con- 

 dition, had received an injury, by which a small portion of 

 its wall had been torn away. The process of reparation of 

 this lesion consisted not of a mere bridging across of the 

 aperture, but of a slight and irregular lateral outgrowth of its 

 margin, and of the partial occlusion of the tube so produced 

 by a coronal plate. This increased in size with the growth 

 of the sponge, and has been the cause of the irregularity of 

 the upper part of the primitive cylinder, which has been 

 already noticed. 



The perfect regularity of the lower part of the tube, the 

 asymmetry of the diverticulum, and the distortion of that 

 part of the parent sponge implicated in its growth, are facts 

 which disprove the hypothesis that this is to be regarded as a 

 normal variety of Euplectella. I have not seen any record of 

 a similar malformation in the literature of the subject, but 

 believe that there is a specimen exhibiting it in the Elgin 

 Museum. My friend, Mr F. Jeffrey Bell, of the British 

 Museum, informs me that there are no branched specimens 

 in the national collection. 



IX. Tlie Old Bed Sandstone, of Shetland. By B. N. Peach, 

 Esq., A.E.S.M., E.G.S., and John Horne, Esq., F.G.S. 

 (Plate I.) 



(Read 19th February 1879.) 



The Old Pted Sandstone of Shetland, though inferior in 

 development to that of Caithness or Orkney, claims special 

 attention on account of the interesting proofs which it affords 

 of the previous extension of that formation, as well as the 

 remarkable history of the volcanic phenomena which charac- 



