16^ THE GEOLOGIST. 
westerly dip. In the yellowisli and dark brown clay near tlie 
uppermost part of the section at Gay Head, and in the green 
sand immediately resting npon it Mr. Lyell found the teeth 
of a shark, that of a seal, vertebrse of cetacea, crustacean re- 
mains, and casts of Tellina and My a. These prevail at intervals 
through a thickness of nearly 100 feet, and are followed by beds 
of sand and clay with lignite. Mr. Lyell found no remains in 
the red clays. Many rolled bones were found in the osseous 
conglomerate. 
In the section at Chilmark similar strata to those at Gay 
Head occm', but the general dip is south-west. Some of the 
folds, however, give anticlinal dips to the north-east as well as 
the south-west, and there are many irregularities, the beds being 
sometimes vertical and twisted in every direction. Several faults 
are seen, and veins of iron-sand, which intersect the strata Kke 
narrow dykes, as if there had been cracks filled from above. 
One bed of osseous conglomerate at Chilmark, four yards in 
thickness, is vertical, and its strike is well seen to be north 25^ 
so that the disturbances have evidently been so great that 
it would be difficult without more sections to determine posi- 
tively the prevailing strike of these beds. The incumbent drift is 
very variable in thickness, and large erratic blocks, fi'om twenty 
to thirty feet in diameter, are seen resting on quartzose sand. The 
author saw no grounds for concluding that any cretaceous strata 
occur anywhere in the island, nor could he find any fossils which 
appeared to have been washed out of a cretaceous formation 
into the tertiary strata, as some have suggested. 
Mr. Lyell proceeds to the consideration of the organic re- 
mains collected by himself in Martha^s Vineyard. 
Mammalia. — 1. A tooth, identified by Prof. Owen as the 
canine tooth of a seal, of which the crown is fractm-ed. It 
seems nearly allied to the modern Cystophora proboscidea. 
* Nos. 5 aiid 6 of Prof. Hitchcock's section. 
