On the Tertiary Strata of Martha's Vineyard. 319 



found the teeth of a shark, that of a seal, vertebrse of Cetacea, crusta- 

 cean remains, and casts of Tellina and Mya. These prevail at intervals 

 through a thickness of nearly one hundred 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 occur, 

 but the general dip is southwest. Some of the folds, however, give an- 

 ticlinal dips to the northeast as well as the southwest, 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 like 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° 

 east, so that the disturbances have evidently been so great that it would 

 •be difficult without more sections to determine positively the prevailing 

 strike of these beds. The incumbent drift is very variable in thickness, 

 and large erratics, from twenty to thirty feet in diameter, are seen resting 

 on quartzose sand. The author saw no grounds for concluding that any 

 cretaceous strata occur any where in the island, nor could he find any 

 fossils which appeared to have been washed out of a cretaceous forma- 

 tion into the tertiary strata, as some have suggested. 



Mr. Lyell proceeds to the consideration of the organic remains col- 

 lected 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 fractured. It seems nearly allied to 

 the modern Cystophora proboscidea. 



2. A skull of a walrus, differing from the skulls of the existing species 

 ( Trichecus rosmarus, Linn.), with which it was compared by Prof. Owen, 

 in having only six molars and two tusks, whereas those of the recent 

 have four molars on each side, besides occasionally a rudimentary one. 

 The front tusk is rounder than that of the recent walrus. 



3. Vertebras of Cetacea, some of which are referred by Prof. Owen to 

 the Whalebone whales, and others to the Bottle-nosed (Hyperoodon). 



Pisces. — Teeth of sharks resembling species from the Faluns of Tou- 

 raine, viz. Carcharias megaladon, Oxyrhina xiphodon, 0. hastulis, and 

 Lamna cuspidata. With these were large teeth of two species of Car- 

 charias, one resembling C. productus, a Maltese fossil. With the excep- 

 tion of the two last, Mr. Lyell found the same species in meiocene strata 

 near Evergreen, on the right bank of James River in Virginia. 



Crustacea. — A species considered by Mr. Adam White as probably 

 belonging to the genus Cyclograpsus, or the closely allied Sesarma of 

 Say, and another, decidedly a Gegarcimus. 



