450 SHIMER. 



Notes on Species. 

 Plants. 



The peat encountered in the various sections is probably entirely 

 of fresh water origin. After an examination of the peat from the 

 subway at Exeter Street, Mr. G. B. Reefl of Harvard University 

 writes : 



"I find no plants or remains of plants such as now grow on salt 

 marshes or anywhere below high tide level. But what species have 

 entered into the formation of the peat I can not determine beyond 

 the presence of grasses and sedges, probably both tops and roots, 

 woody roots probably of some Ericaceous plants, and fragments of 

 wood. A large part, however, is made up of much decomposed 

 material now unrecognizable. It has apparently, too, undergone con- 

 siderable compression as all the stems are flattened. " 



The peat at Church Street, the deepest encountered, was also of 

 fresh water origin, and occurred similarly beneath the black silt. 



Spongia. 



Cliona sulphurea. — The specimens noted at the Berkeley Street 

 locality were almost entirely in oyster shells. 



Bryozoa. 



Membranipora pilosa. — This form is comparatively abundant at 

 Exeter Street upon the larger shells of My a arenaria, less so upon 

 Modiolus demissus, var. plicatulus. 



Pelecypoda. 



Ostrea virginica. — This, our only species of oyster, is very rare at 

 Exeter Street, being represented by but three specimens, the largest 

 of which is only 85 mm. lon^ by 70 mm. broad. At Charles River 

 this shell is exceedingly abundant including both the long, narrow 

 or so-called "current" form and the short, broad "quiet-water" 

 form. The most usual size of the former is 230 mm. in length and 

 55 mm. in breadth; of the latter the length is 130 mm. and the breadth 

 70 mm. At Berkeley Street the very large current form is common 

 at a depth of 27 to 31 feet. A valve of one of these, an old individual, 



