NOTES ON CAMBRIAN FAUNAS 
479 
sheathed tubes do occur quite abundantly on one layer and are 
not obvious on another closdv above or below instances of en- 
sheatbing can be found in layers where the single tubes of 
S. pulchella abound. 
Mr. Walcott in his studies on the Cambrian Faunas of North 
America — Bull. 30 U. S. 'Geological Survey, Plate XIII, fig. 2, 
shows a good example of this ensheathing of S. rugosa , showing 
apparently no less than ten tubes one with another. This is an 
unusual number, and can hardly be attributed to accidental con- 
ditions ; the specimen is from Arise ail Loup. 
If I am right in my explanation of the cause of the annula- 
tions in lS\ rugosa . it will be necessary to retire this name or that of 
A. pulchella. In Billing’s publication of the two species X. rugosa 
stands first, hut as the name in my view is based on a misappre- 
hension of the characters, and is erroneous in its meaning, it 
would seem that pulchella should be adopted. 
But in fact the whole genus Salterclla of Billings is based on 
an erroneous view 'that these shells were species with strong 
annulations like Serpuihtes. " Salterclla ” pulchella is really a 
smooth shell, and a strong glass is required to make visible the 
very fine concentric striae which encircle the shell. 
These regular concentric striae, the round tube a little flatten- 
ed on one side and the slightly bell shaped aperture show that 
in pulchella we are dealing with a species of Orthotheca. Num- 
erous examples show that the species was came rated ait the 
proximal end by several diaphragms, convex downward. In 110 
instance have we found an acute point to the shell Which is always 
decollated. If a slender proximal end of rigid substance existed 
it must have been fragile, and broke away when exposed to abra- 
sion in agitated waters. As Billings remarked, the tube had a 
slight curve. This was towards the ventral side. 
Air. Walcott has already removed the remaining species of 
Saiterelila, S. obusa, to the genus Hyolithes. As Salter had 
already named a Theca (—Hyolithes) obtusa , Billings name be- 
came a synonym. Walcott therefore gave a new name too the 
species, calling it Hyolithes Billingsi . This species, or one closdly 
related is found with the Protolemis Fauna in Southern New 
Brunswick. 
