CAMBRIAN DISTRICT OF NORTH ATTLEBORO. 387 



the determination of species. The result was naturally a number of errors. 

 The worst of these was the reference of a small head of some species of 

 Olenellus to the genus Paradoxides. The specimen found was a cast of the 

 lower surface of the chitinous envelope of the head, and apparently showed 

 facial sutures, the nonexistence of which in the genus Olenellus was already 

 suspected at that time. It ■ is now very well known that the position of 

 facial sutures is indicated by grooves on the lower surface of the protecting 

 envelope of the head (exoskeleton), a cast of which could erroneously give 

 the idea of a partial separation of the free cheeks at the facial suture. In 

 spite of this incorrect reference of the cast in question, the fauna was 

 recognized as being of the Olenellus Cambrian horizon. 



In consequence of the discovery of an Olenellus Cambrian fauna in 

 the red shales and limestones southwest of North Attleboro, the red shales, 

 sandstones, and conglomerate farther east, and, in fact, wherever found for 

 miles around, were considered of Cambrian age. Owing to their general 

 westward dip they were even viewed as anteceding the fossiliferous beds. 

 The report, however, had scarcely been published when, early in 1889, the 

 writer found loose bowlders of red sandstone with well-preserved specimens 

 of calamites in the hills southwest of the southern end of the reservoir pond 

 south of North Attleboro. In consequence all the red shales, sandstones, 

 and conglomerates just described as Cambrian, excepting the shales 

 occupying the valleys of localities 1, 2, and 3, were referred to the Carbon- 

 iferous. In the writer's thesis, On the Igneous and Metamorphic Rocks of 

 the Narragansett Basin (Harvard Univ., 1890), these red phases of the 

 Carboniferous were described as a group of the Carboniferous, the Wamsutta. 

 After this thesis had been presented, in the spring of 1890, Cordaites leaves 

 were found in situ, west of the road, two-thirds of a mile southwest of 

 the reservoir pond. At a later date Mr. J. B. Woodworth discovered 

 abundant stems of calamites in an exposure on the north side of the road to 

 Attleboro Falls, about two-thirds of a mile southeast of the North Attleboro 

 post-office; and finally, in 1895, the writer found a poorly preserved specimen 

 <jf calamites in the arkose beds in the northwestern part of North Attleboro, 

 north of Division street. 1 



The result of these discoveries has been of considerable importance in 



1 It should be noted that in 1880 Crosby and Barton recognized the Carboniferous age of the red 

 beds in the Norfolk County Basin and inferred from this a similar age for the red rocks about North 

 Attleboro, but they did not discover the fact that a portion of these beds were of Cambrian a^e. N. S. S. 



