1911.] NATURAL SCIENCES OF PHILADELPHIA. 537 



in winter, even down to a much greater depth than is exposed by the 

 receding tide, the firm character of the clay may be due in part to 

 the effect of ice pressure, but this clay deposit was doubtless covered 

 bj' the sand and gravel of which a remnant remains in the raised 

 ground on the Point, and this being some 20 feet thick would have 

 compressed the clay to the firmness which it exhibited upon these 

 flats. To the northwest of our camp it was beautifully rippled for a 

 mile or more and for the full width of the flats. The sandy strand 

 on the west side of Dove Point was also rippled with each tide. 

 I thus had an excellent opportunity to study the formation of 

 water-formed ripple-marks and other impressions made upon this 

 clay surface, and I was at once struck by their close resemblance to 

 similar markings so common in the continental deposits of the 

 Triassic of the State of Pennsylvania, which I had studied while 

 connected with the Geological Survey of that State. Other mark- 

 ings on these clay surfaces closely resembled the tracks and trails 

 described and figured by Hitchcock in the rocks of this age in the 

 Connecticut Valley. 1 Their origin on these mud flats could readily 

 be seen and, as they so exactly resemble the formations found in the 

 rocks, a description of them may throw some light upon the markings 

 observed by Hitchcock and others. 



No living mollusks were seen on the mud flats, being doubtless 

 killed by the freezing of the bay in winter, but species of Mya are 

 evidently living in the deeper water of the bay, as their shells were 

 occasionally encountered in places where they had been stranded 

 by the tide. To the east, towards the Mealy' Mountains along the 

 shore, a few specimens of gastropods were seen, some three or four 

 miles down the bay. 



While mollusks are rare, the sea weeds in some parts of the bay 

 flourish in great luxuriance. Where the shore is rocky and the 

 bottom is composed of sand and shingle rather than clay, as is the 

 case to the east side of the bay, especially from East Arm to Cart- 

 wright, and, in fact, along all the shores examined where the condi- 

 tions were favorable, the bottom is covered with a dense growth of 

 Fucus, probably F. vesciculosus L.. which here attains a height of 

 three or four feet and forms dense masses of several feet in diameter. 

 In the deeper water, especially in the channels, are seen the broad 

 fronds of Laminaria longicrucis De la Pyl., extending up from the 

 bottom and the laminae waving about in the current. When seen 



1 Edward Hitchcock, Ichnology of New England, 1858; Supplement to the 

 Ichnology of New England, 1865. 



