PLEISTOCENE FORMATIONS OF SANKATY HEAD 727 



Martens, and Pandora crassidens Conrad, was a surprise, as the first 

 two belong to the arctic fauna of the Pacific coast and, according 

 to Dall, have not heretofore been found east of Point Barrow, while 

 the last is common in the Miocene of Maryland, and, according to 

 the same authority, has not previously been found above that horizon. 

 It does not seem possible that the Pandora could have been derived 

 from an older bed, as all the other species are distinctly Pleistocene; 

 and in case the material from an older bed had been disturbed and 

 redeposited, we should expect to find a number of associated species. 

 Moreover, the two left valves found were entirely free from any trace 

 of an old matrix, were no more worn than the other fossils from the 

 same bed, and were of the same color and general appearance. It 

 would seem, then, that Pandora crassidens Conrad has in some 

 localities continued on into Pleistocene times. The two Pacific 

 species would seem to indicate that in Pleistocene times the "North- 

 west Passage" was more open than at present, and perhaps also 

 that in the interglacial period in which these beds were deposited 

 the ice had entirely disappeared from even the northern part of the 

 continent, so as to leave the channels along the coasts of that region 

 free from ground ice. 



A single specimen of the rare species Chrysodomus stonei Pilsbry 

 was found, which was first reported and described from specimens 

 washed ashore from supposed Pleistocene beds under the sea, off 

 the southern coast of New Jersey. This, and the Miocene Pandora, 

 are the only species yet found occurring in these beds which are 

 now extinct. 



It has been a matter of comment, that not a single Pecten has 

 heretofore been found at this locality in beds furnishing in abundance 

 such species as Ostrea virginica, Venus mercenaria, and My a arenaria. 

 In looking over a quantity of material from the "upper shell bed," 

 a two-inch shell fragment was found which seems to be clearly identi- 

 fied as from near the ventral margin of a specimen of our northern 

 species, Pecten magellanicus Conrad. 



Modiola hamatus Verrill is mentioned in former reports as com- 

 mon in the "lower shell bed," and was found in association with 

 Mytilus exustus Linn, from which at times it is difficult to distinguish. 

 It is probable that the latter species has been mistaken for Modiola 



