424 AV. ^l. DAVIS AND S. W. LOPER — FOSSILIFEROUS TRIASSIC SHALE. 



points. The extreme poiuts now identified in this bed are about fifteen miles 

 apart, and ten well proved faults occur between them. 



Another bed of dark shales with impressions of fish and plants has been 

 known for many years in a small brook north of the village of Westfield, 

 Connecticut, and about half a mile southwest from the station of that name 

 on the Berlin-Middletown branch of the New York, New Haven and Hart- 

 ford railroad. This lies about one hundred and fifty feet below the posterior 

 trap sheet, or about a quarter way from the posterior to the main sheet. It 

 will be referred to as the posterior black shale. Outcrops of what seems to 

 be the same bed have been opened at four difi[erent places, the distance be- 

 tween the extreme points being about fifty miles, including twelve or more 

 faults. Its position is everywhere two or three hundred feet above the main 

 trap sheet. 



A more precise statement of the location of the fossiliferous strata and a 

 provisional list of the fossils found in them is presented by Mr. Loper. 



On examining the tables of species as made out by Mr. Loper, there ap- 

 pears to be good reason for concluding that difl^erent outcrops of the two 

 beds of shale might be distinguished as belonging to two horizons on paleon- 

 tological grounds alone ; but it should be borne in mind that there is still 

 much possibility of finding various species, now known only from one of 

 the beds, in the other. The large number of species from the old Durham 

 locality means in part good conditions for their preservation, but it means 

 also that this locality has been more carefully worked and for a longer time 

 than any other. It may also be suggested that while the stratigraphic cor- 

 respondence of the several outcrops of the anterior and posterior shales was 

 very satisfactory, so far as determination by rough pacing measures would 

 determine, it is quite possible that they do not represent precisely equivalent 

 horizons, although they are certainly as nearly equivalent as the so-called 

 geological horizons commonly are. It is not unlikely that there may be 

 several fossiliferous layers at slightly different horizons of the anterior and 

 posterior shales, and that our openings touch one of them at one point and 

 a second at another. Indeed, it may be that there are various fossiliferous 

 black shales scattered through the formation, yet not visible owing to their 

 Aveakness and the heavy drift cover that so effectively blankets over the 

 surface; but the main question of the repetition of certain fossiliferous beds 

 at definite positions in the various faulted blocks seems to be settled. The 

 occurrence of the two shales at predicted localities and the correspondence 

 in the fossils of each horizon at various localities so fully conform to the 

 requirements of the theory of the faulted monocline that this structure may 

 now be regarded as established for Connecticut on paleontological as well as 

 on structural evidence. 



Harvard College, Cambridge, Mass., December, 1890. 



