MUSEUM OF COMPARATIVE ZOOLOGY. 23 
hundreds of feet, belonging to the Paradoxides section of the Cambrian, 
exists on the southern shore of Massachusetts Bay in the township of 
Braintree. This deposit probably extends, as a continuous mass or as 
an isolated section, as far as the Neponset River in Quincy, a distance 
of about four miles. Although no distinct fossils have been found, save 
at Braintree, a number of distinct remains occur near the Neponset 
River, in beds having much the same aspect, and apparently at about 
the same distance from the syenites, as those at Braintree. It there- 
fore, on account of the large extent of the Paradoxides section about 
Massachusetts Bay, seems possible that the Braintree section may be 
represented somewhere in the Attleborough Cambrian district. 
Although I spent a good deal of time searching for rocks which should 
have a physical likeness with those at Braintree, I have not yet been able 
to discover any such in the Narragansett field. The conditions under 
which the search was made render it difficult to make sure that such 
deposits may not yet be found in that vicinity. A search for the Attle- 
borongh series in the Boston synclinal and in the neighborhood of the 
Braintree beds has likewise been unavailing. No deposits of conglom- 
erates or sandstones having the peculiar hue of that series have been 
found in any part of the Boston basin. I therefore regretfully conclude 
that the probability of determining the relative position of these two sec- 
tions in this field is small. The absence of one of these members of the 
Cambrian series from the Boston basin and from that of Attleborough 
may be fairly attributed to the large amount of erosion to which both 
regions have been subjected. The Paradoxides beds of Massachusetts 
Bay are evidently a mere remnant of a sheet which once overspread a 
large part of that area. The extensive conglomerates belonging to the 
Roxbury series, with their associated slates and the argillaceous deposits 
of Cambridge and Somerville, are probably of Cambrian age, and may 
possibly belong to the lower portion of that section, along with the Para- 
doxides bearing strata. But it is barely possible that they may repre- 
sent the same age as the conglomerates and shales which lie above the 
level of the Attleborough fossiliferous horizon. The wide difference in 
the mineralogical character especially of the slates makes this view, how- 
ever, improbable. 
Although the relation of these two horizons is not determinable by a 
comparison of the Massachusetts Bay and Narragansett deposits, it is 
possible that it may be elsewhere determined. Fragments of sections 
containing these horizons may well be found along other portions of our 
Atlantic coast. 
