TUTE: ON AN OETHOCEEAS OF THE MILLSTONE GEIT. 83 
But the most interesting feature is the occurrence of two 
well-marked semi- oval lobes in two specimens in my posses- 
sion. These lobes lie one on each side of the lower part of 
the wide chamber (Fig. 1, 2 c), and appear to me to be the 
fossil-marks of fins. There are, however, no other indications 
of structure than the form, which is well defined in its outline. 
The lobes also are not flat, but slightly rounded, so as to 
cause a distinct depression upon the shale in which the 
fossils lie. 
If these are the fossil marks of fins, it would indicate that 
these shells were internal. The exceedingly delicate structure 
of the large chamber points also to the same conclusion. 
The larger forms of the Orthoceratidae are generally sup- 
posed to have been external shells ; and allowing this to have 
been the case, it is perfectly consistent with what we know 
of other mollusca to believe that there were other forms of 
the Cephalopoda in which the shell was internal, but built 
up upon a plan analogous to that of external shells. 
GOBDALE SOAK (see Photograph). BY THE EDITOE. 
The photograph issued with this volume of Proceedings 
represents one of the finest mural escarpments in the North 
of England. It is difficult to realise the terrific grandeur of 
the Limestone Cliffs which rise on each side the gorge; some 
idea may be formed, however, by noting the relative size of 
several of the members who may be discerned occupying 
various positions on the rocks near the waterfall. (The 
photograph was taken by Mr. Wormald, in 1877, during a 
visit of the Society to Malham and Gordale.) The cliffs are 
about 300 feet in height, in places perpendicular, but 
generally the upper part overhangs to some extent, the lower 
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