1 
io6 Ulrich on Correlation of the Lower Silurian. 
Beds III. The lower layers of this division, which com- 
prises about loo feet of mainly gray to light drab limestones, 
closely resemble the heavy, tough beds of division I. Some 
are rather brittle and break with a conchoidal fracture. The 
gray layers are commonly thin-bedded and slightly crystalline. 
The middle layers are of drab color, variously bedded, very fine 
grained, rather soft, with frequent crystals of calcite and occa- 
sional specks of iron pyrites. Toward the top the beds become 
shaly, of a light dove color, and highly fossiliferous. The top 
is marked by a gray crystalline layer two or three feet thick, 
plated on the upper side with several thin layers of red chert, 
almost made up of the valves of Leferditia fabidites. 
In the lower heavy bedded layers, fossils are very few, but 
near High Bridge several good fragments of undetermined 
trilobites were found. They belong to four species, one an 
Asaphus^ the others apparently referable to Bathyiirus. One 
of the latter is identical vv^ith a form found 150 feet or more 
below the top of beds I, while another recurs high up in the 
present beds. The middle layers are almost destitute of fossils, 
but the peculiar markings which Hall has described under the 
name Phytopsis tiibulostim are abundant. Higher vip, Phytop- 
sis celhilosum Hall, which is clearly a lax-growing form of 
Tetraditim, is met with. The upper twenty feet or shaly por- 
tion of the beds, are highly interesting to the palaeontologist, 
as they contain thin plates of limestone literally filled with 
organic remains. The fossils, too, arc in an exceptionally good 
state of preservation. The following should be mentioned : 
Tetradiiim celhdosum Hall sp. Pleurotomaria subcoiika Hall. 
Ptilodictyii raiiiosa Ulrich. Helicotoma n. sp. 
" Uhana Safford. Trochonema umbilicatum Hall 
Stictopora labyriuthica Hall Ormoceras tennifilum Hall. 
" ukliolsoiii Ulrich. Orthoccras multkameratnm Hall. 
Phyllodktya froiidosti Ulrich. " aiiiplicaiiicrafum Hall. 
Helopora spiniformis Ulrich. " four undet. species, one 
Phylloporina (a species near or with strong annulations 
identical with /*. (reiifonoisis.) Cyrtoceras phniodorsatiim Whitfield. 
Nicholson. " hondi Safford. 
Montktdipora xvefheyhyi Ulrich. Rndoceras sp. 
Ho7iiotrypa rnmulosa Ulrich. Conularia quadrata Walcott. 
Or this suhcqiiata Conrad. Ptevofhcca at ten 11 at a Hall. 
" tricotaria Conrad. Cypricarditcs vcntrkosus Hall. 
" deflect a " " suhtyiincata Hall. 
Streptorhynchus filitextus Hall. " subcurinatus Bill. 
(The typical form.) Leperditia fabuUtes Conrad. 
Streptorhyuclius filitextus } var. a. " ^ tttmida 11. spf 
(A thinner form.) Beyrichia persctdpta n. sp. 
Subtdites elongatus Conrad. " 'i binirr'ata n. sp. 
