PALAEONTOLOGY : EASTERN MASSACHUSETTS. 51 



of sixteen species, in addition to the bryozoan Hippothoa variab- 

 ilis which encrusts the worm tubes. The layer of clayey ferrugi- 

 nous sand overlying the Serpula bed contains Ostrea virginiana 

 and small specimens of Argina pexata. " The upper shell bed 

 consists of coarse beach sand, with pebbles, slightly intermixed 

 with clayey matter " (Merrill). The " fragment bed " of Mer- 

 rill, or the uppermost fossiliferous stratum (included by Scudder 

 in the upper shell bed), " consists of white quartz sand and peb- 

 bles, with a great abundance of comminuted shells." It differs 

 from the upper shell bed proper in the condition of the fossils 

 and the entire absence of ferruginous matter. 



The strata above the Serpula bed are especially rich in northern 

 species, such as Buccinum undatnm, Ceronia arctata, Astarte 

 castanea, Cyclocardia borealis, Mya truncata, Balanus porcatus, 

 etc., which are common. Many of these are now found on the , 

 outer shores of Cape Cod. 



The total number of species from the three beds, as given by 

 Verrill, is sixty, —most of them mollusca. Thirty-seven species 

 are found in the lower and thirty-six in the upper bed. Only 

 thirteen species are common to the two. 



Merrill has made some additions to this list, and also has 

 shown a greater vertical distribution for some of the species. He 

 regards these deposits as transported material, thus differing 

 from Verrill; who, deducing from the observations of others, re- 

 garded the oyster and Serpula beds as deposited in a shallow bay 

 protected from the outer waters by a barrier, and considered that 

 the upper bed was deposited after the breaking of the bar and. 

 the ingress of the Atlantic waves. 



2. WINTHROP GREAT HEAD. 



Route. — By train, Boston, Revere Beach and Lynn railroad (narrow 

 gauge), Atlantic avenue station, to Winthrop beach, then walk to cliff. 



By electrics, from Scollay square, Beachmont car to Beachmont, then 

 follow shore past Grover's cliff, to Winthrop Great Head cliff. Or take 

 East Boston car via ferry, changing to Winthrop car in East Boston. 



This is the original locality from which Stimpson obtained his 

 recent fossils in 1854. His list included: Balanus rugosus (= 

 B. crenatus), Mya arenaria, Solen ensis (r= Ensatella americana) 

 Mactra solidissima, Venus mercenaria, Astarte sulcata (= A. 

 undata), A. castanea, Cardita borealis (= Cyclocardia borealis), 



