A Geological Section at Todd's Fork, 0. — Foerste. 417 
the geological scales as Silurian rocks. Nor do we believe the practical 
Talue to be very great, because there are many forms of teeth which could 
safely be placed in two or three genera, as far as analogies with living 
genera are concerned. Nevertheless, we believe that the only basis for a 
more practical classification lies in the collection of a greater number of 
fossil forms than now known, and hence we adopt a confesi-edly poor clas- 
sification for the time being. 
OENITES DERIPIENS, SJ). Tl. 
Fig. 2. 
Resembling 0. cuneaUis Hinde, but larger, 2.6 mm. in length. Serrated 
along the upper edge, the teeth directed backwards, about 10 in number, 
the first one or two indistinct, preceded by a vacant space, anterior to which 
arises a large fang-like tooth, whose tip whs broken off in our specimen. 
This tooth does not lie in the same plane with the main body of the fossil, 
but bends toward the left, giving rise to a concave curvature of the body 
of the tooth along its anterior third. A ridge just beneath the row of teeth 
becomes very marked posteriorly. 
ARABELLITES PROCURSUS, Sp. n. 
Fig. 3. 
This species resembles A. ascialis Hinde in the existence of a very small 
tooth introducing a series of larger teeth, but the succeeding teeth are 
much smaller than in our species. A comparison with A. aciculatas James 
of a lower horizon, is more pertinent, but, judging from the published fig- 
ure of that form, the smaller tooth is larger than in our form, and the suc- 
ceeding teeth are irregular in size. It is also considerably larger than our 
form, which measures scarcely 1.8 mm. in length. The curvature of the 
large anterior tooth in our drawing is in part conjectural. The first in the 
row of teeth is quite minute, and is situated at the base of a very large 
tooth, which is the largest tooth in tiie row. The next teeth are successively 
smaller, all of them being directed backwards. There are seven teeth in 
the row, the last seeming scarcely more than undulations on the upper 
edge of the tooth. A very marked ridge running along the body of the 
fossil, from the large anterior fang-like tooth, beneath the row of teeth, to 
the posterior extremity, and an indentation along the base of the tooth, 
causing a part of the same to extend backwards a.s a narrow projection, in 
line with the lower edge of the same, are the only remairung features of 
note. 
LUMBRICONEREITES AUSTINI, Sp. 71. 
Fig. 4. 
This species is quite common and is very distinct from any species 
hitherto described. Teeth from both the left and right side of the mouth 
have been found. The one here figured and described is a left tooth. The 
length is 2. 3 mm. The body is flat, incurved along the left edge and also 
post'-riorly, the posterior border extending to the sixth tooth in the row Of 
teeth. A longitudinal groove along the postero-lateral border of the body 
is its only prominent feature. Along the left edge is a high, sharp ridge, 
quite straight along the serrations, but curving decidedly at its anterior 
