Lower Potsdam Rocks at Troy, N. Y. 135 
The limestones of c, which I have for convenience sake desig- 
nated simply as limestones 1, 2, 3 and 4, are those already re- 
FIUD SOM RIVER 
a, yan ni of the Hudson gh ioenensens ho Ae — eh 7: 
and graptolite species Tr at Dry Rive Fr, esac 
b. Black al shales with thin layers “of Bet holding gra: i fo most sores 
of either the Hudson River or Utica forma 
c. Slates, sandstones, nestoties ‘aa limestone isigeioiinedtat of the Lower Pots- 
1-2. Conglo merate limestone interstratified hays coarse slates. 
3-4, Even-bedded limestone similarly situa 
ferred to as being the only portions of the Lower Potsdam at 
Troy that have proved fossiliferous. The annexed table pre- 
sents a list of the species obtained from them so far as described ; 
and shows also the manner of their distribution among them. 
Table showing the distribution of the fossils in the Lower Potsdam group at Troy, N.Y. 
| 
Limestones, 1/2)3 4| 
1, Archzeocyathellus Rensselaericus® - ------------------ oie Pies 
2. Obolella desqnamats BRR RES 0S SEP * Pk] LK 
S. -. -* othe...) ee thdeeee ee _- [KK]. 
4. it obelaty ei ee eee ee Pah be ae ake, - 
5. 5 Sitti U5 OF eu eee ee ea rae de 
6. Stenotheca rugosa.....--.--------+-----00°0770777 * bk LK Lok 
7. Mel volta ck fcc) eee ee a ate x pak pk |e 
8. Hyolithellus SiN. oo ck 2 as be eae caus * 1K LOK LK 
lithes Americanus......---------------------"" .-)>* | kD 
1 ce maw erg 5° i ee eae a.|>* | K | * 
ll “ he Cpe ee wae bee 26, ae. 
12. Leperditia Troyensis..--..-..-----------<-=+""--"* ci loeer ie 
13 Microdiscus s Sei oh 2 ot Set ne ale ae aoe tem _-| | K) OK 
14, “ s+ eet Tiere ao : ‘ 
15. Conocephalites wie nds nega Pe eS Fe a 
16. Olenellus — ee ~-| >} >K|* 
it. Aghostus nobilis.2.......-.: --sesseee-9+---"*239"" Sulonpest 
18. Bivalve of vinden relations... ---------------- 6K Ei iad 
It will be seen from the above table that out of the eighteen 
Species enumerated, thirteen are common to limestones 8 and 4; 
* This species was described in the March No. of this Journal for om Loge 
Lavy and referred by me provisionally to the genus 
ider it entirely distinct from that genus, an d have ne here the gene- 
t cha: f A are th 
+ This species equals th stus lobatus of Hall (Pal. N. Y., vol ip. 268, pl. 
xvii, figs. 5 a-f ), and appears to me to belong to Mi 
tus, It occurs in + numbers in the limestones at euike. but I hai ae seen 
4 Specimen of it showing all the parts in connection 
