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THE LlFE-HISTOEY OF NUCULA DELPHINODONTA. 3l3 



The Life-History of Nucula delphinodonta 

 (Mighels). 



By 



Crilman A. Dreiv, 



Professor of Biology, University of Maine, Orouo, Me. 



With Plates 20—25. 



The material upon which these observations were made 

 was secui'ed at Casco Bay, Maine, during the summers of 

 1897 and 1898. Nucula delphinodonta is a small form, 

 seldom growing to be more than 4 mm. in length, and as it 

 lives below low-tide mark it is not very well known by col- 

 lectors. By using a sufficiently fine dredge, however, un- 

 limited numbers of adult and young specimens may be 

 procured. Individuals may be found living under very 

 different conditions; in inlets and protected places, and ex- 

 posed to the open sea, and from near low-tide mark to a 

 depth of several fathoms. The principal habitat, however, 

 is in the shallow inlets and near the heads of sounds, where 

 the bottom is composed of fine mud, mixed with some sand, 

 broken shells, and decaying vegetable matter. Individuals 

 are most numerous just outside of the eel grass which skirts 

 the shore where the bottom is of this character, in water 

 which at low tide is from one to three fathoms deep. The 

 mud in which they live is much like that inhabited by 

 Yoldia limatula, except that it is not so free from shore 

 debris. Although some specimens may be obtained where 

 Yoldia is most abundant, they are generally more numerous 



VOL. 44, PART 3. NEW SERIES. X 



