Silurian Land Plants from Ohio. — Foerste. 137 
9 occupy a length of 4 mm. The striae near the lower side of 
each scar follow the crescentic outline of the bounding ridges, 
becoming less curved above. On careful examination it will 
be found that in some cases the bounding ridge is not distinctly 
defined. The striae of one scar will run over into and be contin- 
uous with those of the next lateral one. At the point where 
the defining ridge ought to occur laterally, these striae curve 
strongly forward, and are massed closer together, forming an 
elevation, the extreme form of which is the usually strong 
elevated bounding ridge. Even where this crescentic ridge is 
sharp and distinct, the stria? can be traced across the same ; 
in this case the flexure of the stria 1 is often less where crossing 
the ridge, and it is not so evident that the ridge is not an 
autogenous product, perfectly distinct from any more marked 
curving and massing together of the striae. It is believed, 
however, that these fossils are nearest related to those species 
of Cyrtoceras ornamented by horizontal stria* and are a 
variety of that type, due to peculiar irregularities of growth 
at the aperture which caused frequent and regular concave 
emarginations of the edge, successively and more or less 
gradually, alternating in position, some disappearing, others 
arising in intermediate places, thus giving rise to the peculiar 
imbricated scar-like areas so characteristic of these shells. 
There is no doubt of the congeneric relations of the Brown 
and the Huffman specimens. The case of the Eaton Glm>t<>- 
dendron is much less certain, owing to the small size of the cast 
and the absence of all indication of the interior structure. It 
is a cast of a fragment of the exterior surface and does not 
present the more detailed structure of the area of the scar. 
Attention is called to the following details: The crescentic 
ridges bounding the lower side of the scar areas are strongly 
curved, in fact they are practically semi-circular. The ridges 
are much more strongly defined above; or the scar there meets 
the ridge at the base of a rather abrupt declivity, while the 
areas below meet on a more inclined slope. The area of the 
immediately (vertically) lower scar rises anteriorly, at times 
ascending regularly as far as the middle of the defining ridge 
of the succeeding scar, thus lessening the definition of the 
ridge at that point. Owing to the greater rise of the middle 
ridge above the general level of the area of the sear above it. 
