BULLETIN OF TlIE NATURAL HISTORY SOCIETY 
1 7 8 
Thu piece of limestone sent contained abundant remains of 
the Salterdlas with pants of trilobites including those of Olenellus 
Thompsoni. 
The aspect of t'he surface of layers of this rock is well shown 
in the wood cut. Fig. 22, page 17, of the first volume of Billing’s 
Palaeozoic Fossils representing Sal ter cl I a rugosa, Bill. 
M«r. Billings does not mention that these fossils are preserved 
in phosphate of lime, which however is the case. As a result 
of the wasting of the limestone from exposure to the weather 
these fossils stand out prominently from the surface and are 
readily examined. 
On examining these “Saiterellas” carefully it was observed 
that there was no uniformity in the position of the tube within 
tube that Billings had observed for they were sometimes on one 
side of the outer tube and sometimes on the other. It is true 
that in the majority of cases the ensheathed tubes were similar, 
but in one a young A. obtusa was found in one of the rounder 
tubes referred A. rugose, and one was led to surmise that the 
supposed sheaths were really independent individuals that had 
slipped, one within the other and so given rise to the appear- 
ance of a tube consisting of sheaths. 
A similar condition exists in the tubes of Hyolithes excellens 
Billings found in -the upper limestone at Smith Sound, New- 
foundland, and of about the sarnie geological age; there this 
condition of tube within 'tube is quite common, and the writer 
has suggested that the younger 1 shell had a habit of taking 
possession of a dead shell, for the purpose of a firm support on 
the sea bottom. Whatever the cause, this phenomenon is 
exaggerated in “Salterella” rugosa, which is more frequently 
ensheathed that H. excellens and often shows four tubes, one 
within the other. 
W hen we come to consider these tubes separately we find that 
we are dealing with a form 'which does not differ in any respect 
from S. pulchella, Billings. One s-hould nolt overlook Mr. 
Billing’s remark (page 18) that this species and S. rugosa are 
not in the same bed, and that the two species are not found 
together in the same fragments of rock. But while the en- 
