208 



observe that the chief invertebrate inhabiting this water to-day 

 — Limulus — is one of the nearest living allies of the primor- 

 dial Paradoxides entombed in the bordering slates. 



On White's Neck and along the Monatoquot Hiver the strike 

 of the slate is approximately E.-W., varying to N. 70° E. ; and 

 the dip is 75°— 90° on either side of the vertical. The general 

 resemblance at most points to the slate of the trilobite quarry 

 has been noted. Near the granite some sort of alteration may 

 usually be detected. In the railroad cuts north-east of Wey- 

 mouth Landing the slate is very shaly, soft and unctuous, and 

 with glistening surfaces, especially in the vicinity of the quartz 

 veins, which are numerous. The fresh surface is black, but 

 becomes bronzed by exposure. One principal set of joint 

 planes produces a sort of cleavage parallel with the bedding. 

 The slate is backed on the south by granite, which comes at 

 some points quite up to the railroad ; and the contact is extremely 

 irregular. As remarked by previous observers, the granite is in 

 part clearly exotic ; and the adjacent or enclosed slate is some- 

 times of flinty hardness. The slate is much faulted on a small 

 scale, but is comparatively free from folds and contortions. 



The vertical position of the slates of the narrow band in 

 question indicates a very great lateral contraction, during the 

 period of disturbance, not only of the slates themselves, but also 

 of the underlying granite ; and this is another proof of the 

 former plasticity of the last-named rock ; though it is conceive- 

 able that the same effect might result in part at least from a 

 series of faults converging downwards. 



Quincy and Milton. — Between the granite of Quincy Neck 

 and the belt of conglomerate one mile farther north, as already 

 observed, there are no croppings, except in the angle 'on the 

 west of the Old Colony Railroad. Here the slate strikes E.-W. 

 with vertical or high southerly dips. At points it is thoroughly 

 indurated, and the relation to the granite is substantially the 

 same as farther south. The conglomerate band just mentioned 

 marks an anticlinal axis ; but what the structure may be be- 

 tween this and the supposed anticlinal of North Weymouth and 



