Chcetetes in the Devonian Strata. — Rominger. 57 
modifications constituting the distinctive marks upon wliicli the 
:separationof Cliatetes tvom. MonticuJ ipo ra , tSfmopora, etc., is based. 
In Monticulipora and Stenojiora the walls of the intimately united 
tubes are either distinctly double, exhibiting a central demarcating 
line between the contiguous walls, or this line is obliterated, but 
each of the tubes is in the immediate circumference of its orifice 
surrounded by concentric rings of darker shade than the lighter 
colored intermediate sclerenchj'mal mass, which plainl}- indicates 
the original independence of each of the anchylosed walls. 
In only a. small subdivision of the Montioilipm-a group are the 
walls so thin that it is practically impossible to demonstrate 
their duplicity. 
Stenopora has double walls like Monficidipora. but among 
other differences the periodical swelling and contraction in the 
thickness of the walls constitutes its principal generic peculiarit3^ 
In CTiafefps the walls intervening between the tube channels are 
comparatively thick, but appear to be common to the contiguous 
X3hannels ; it diflfers further from the other generic groups by the 
development of irregularly disposed longitudinal crests within its 
tubes. Their number is variable; in some of the tubes no crests 
^re observable, in others one, or two, or even three and four 
may be present which indentations cause consideralile irregularity 
iu the shape of the orifices. Another essential point of difference 
between Chcetetes and the other forms under comparison is said 
to be the multiplication of its tul^e channels during the progress 
-of growth by a division of the older tubes, while in the other 
genera the tubes are multiplied by production of lateral gemmae. 
This assertion is at least not fully correct; on the one hand I 
have before me sections of typical Chintetes in which a multiplica- 
tion of the tubes h\ gemmae, sprouting from the edges of the 
tulie walls, is plainly exhibited; on the other hand an indubitable 
instance of a division of the older tulie channels in two, or sev- 
eral, never occured to me, but not very rarely I have seen in 
transverse sections the longitudinal crests project so far into 
the lumen of the tubes that sometimes two opposite crests almost 
■came in contact, which case might he apprehended as a not full}" 
accomplished stadium of the division of a tube. 
The above mentioned want of differentiation in the walls of the 
adjoining tube channels, does not imply their perfect homogeneity; 
in reality every tube orifice is bordered l)y a circle of nodules 
