2i6 The American Geologist. ^p''^- ^^^^■. 
The strong constriction of the aperture, which points to fomis 
Hke Lepadidse and Balanidoe, combats the latter possibihcy. 
SessiHty remains then alone the alternative. In regard to this 
habit I would like to add that our considerable New York 
fauna suggests the occurrence of two different methods of ^^es- 
sility of these organisms. We have, on one hand the rather 
large turbinate types of Gomphoceras, which find their princi- 
pal development in the Schoharie grit, Hamilton shale and also 
in the Goniatite limestone. These clearly give the impression 
of having been planted vertically in the mud with their 
apical portions, the expanded portion resting on the surface 
of the bottom. On the other hand, however, we have lately be- 
come acquainted with a relatively rich fauna of small, slightly 
curved, in general talon-like types of Poterioceras in the 
Guelph beds of New York, and similar forms are known from 
the Chazy and Trenton limestones. These are obtained from 
beds which are coralligenous. They are characterized by their 
relatively small size, their tendency to assume curved and bi- 
lateral symmetric shape, and above all, the fact of their fre- 
quently discarding or losing the greater part of the conch, so 
that only a few of the last camerae are found adhering to the 
living chamber. These peculiarities appear to point to a differ- 
ent mode of life and, in connection with their occurrence in the 
coralligenous beds, suggest that they may have lived in the 
cavities of the reefs themselves, just as living cephalopods hide 
themselves in rocky caves. 
ANNOTATIONS. 
By John M. Clarke. 
Essential to professor Jaekel's conception of fixation in 
Orthoceras, seems to be the assumption of a conchiolin proto- 
conch. The existence of this structure in such form can not 
be regarded as demonstrated. Professor Hyatt was not pre- 
pared even after a close study of the putative calcified Orthoc- 
eras protoconch described by the writer, to grant that it apper- 
tained to that genus. Confirmatory evidence was at that time 
lacking, — it was the only recorded instance of an Orthoceras- 
like shell in which the protoconch was retained, and the object 
could not be generically interpreted from its intrinsic char- 
acters. The presumption, in view of the examples brought 
