188 Mr. Lyell on the Tertiary Strata of Martha's Vineyard. 



Cetacea, crustacean remains 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 

 occur, but the general dip is south-west. Some of the folds, how- 

 ever, 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 

 ironsand, 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 de- 

 termine positively the prevailing strike of these beds. The incum- 

 bent 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 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 remains 

 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 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. Vertebrae of Cetacea, some of which are referred by Prof. Owen 

 to the Whalebone-whales, and others to the Bottle-nosed (Hy- 

 peroodon) . 



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

 Touraine, viz. Carcharias megalodon, Oxyrhina xiphodon, O. hastulis, 

 and Lamna cuspidata. With these were large teeth of two species 

 of Carcharias, one resembling C. productus, a Maltese fossil. With 

 the exception of the two last, Mr. Lyell found the same species in 

 miocene 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 Gegarcinus. 



Mollusca. — 1. Casts of a Tellina allied to T. biplicata, a miocene 

 fossil, and of another near T. lusoria. 2. Cast of a Cytherea resem- 

 bling C. Say ana, Conrad. 3. Three casts of a My a, one of which 

 bears a close resemblance to My a truncata. 



