Prof. Dr. F. Roemer—On the Genus Caunopora. 345 
This relation of Aulopora to Stromatopora, as may readily be seen 
in many Eifel specimens of Stromatopora concentrica, is not likely to 
be equally well observed in the specimens of Caunopora in the lime- 
stone of Devonshire, because these are inclosed in the compact lime- 
stone, and hardly ever show the surface well. 
The structure of Caunopora is not confined to Stromatopora con- 
centrica, but occurs likewise in the Silurian Stromatopora striatella. 
In the drift of North Germany rounded pieces of this latter species 
are frequently observed which are perforated by irregular vertical 
tubes in exactly the same manner as the masses of Cauwnopora pla- 
centa from Devonshire. Goldfuss' has figured a small and not very 
distinct specimen of this kind from the drift of Groningen in Hol- 
land under the name of Syringopora filiformis. Weathered and partly 
decomposed specimens of larger size from Sadewitz in Silesia have 
been described by myself * as Heliolites interstincta. They resembie - 
in fact decomposed specimens of the latter species; but in sections 
_ which I made since, the Cauwnopora-like structure is very distinct. 
In a specimen from the drift at Groningen the horizontal network of 
Aulopora, and above it the vertical tubes of Caunopora, are very | 
clearly seen in connexion. Certain specimens of Stromatopora con- 
centrica from the Hifel offer instances of an animal (when covered 
by layers of the former) preventing itself from being suffocated by 
keeping up small holes through the mass of the Stromatopora. Among 
the many different forms of Stromatopora, those with large tubercles 
on the surface are frequent. Goldfuss has figured them in fig. 8c, 
8d, 8e, and 8f, of plate Ixiv. Hach tubercle is usually perforated 
on the top by a small hole, or sometimes by several holes. 
Now in several specimens it could be ascertained that under every 
tubercle a specimen of Spirorbis omphalodes, the well-known little 
spiral Annelid, had its seat. The hole or the top of the tubercle is 
the opening of the canal by which that little animal kept up its 
communication with the surrounding water, and the tubercle was 
formed by the bending upwards of the successive layers of Stroma- 
topora round this canal. In many cases the tubercles are not 
perforated on the top, evidently because at last the resistance of the 
Annelid had been overcome, and the opening closed by the later 
layers of the Stromatopora. 
In conclusion: The facts which I desire to state in this note are: 
1. Caunopora of Phillips is not a good genus, but is founded on 
masses of Stromatopora which are perforated by vertical tubes not 
essentially belonging to Stromatopora. 
2. The tubes of Caunopora placenta are produced by stems of 
Aulopora repens, which, being covered by the concentric layers of 
Stromatopora, grow upwards in order to keep at least their calices 
open at the surface of the Stromatopora and prevent death from 
suffocation. 
3. The Silurian Stromatopora striatella exhibits also occasionally 
the structure of Caunopora, and in this species likewise the vertical 
tubes are produced by a species of Aulopora. 
1 Petref. Germ. vol. i. p. 113, t. 38, fig. 15. 
2 Diluvial Geschiebe von Sadewitz, p. 24, t. 4, fig. 2c. 
