216 TRANSACTIONS OF THE [1892 



irregular shape, and the spaces between them form 

 numerous dark or shaded recesses, which, during at least 

 half of the time, remain submerged in brackish water, and 

 through which, during ebb and flood tide, its currents flow. 

 Within these recesses, attached to the fragments forming 

 them, the colonies may always be found.* During the 

 sj^ring, summer and autumn months they are also seen 

 upon the exposed surfaces of the dam, upon isolated 

 fragments of slag and brick lying upon the bottom of the 

 stream, and, as also observed by Clark, in Curtis Creek 

 (9, p. 32), attached to the stems and leaves of various 

 species of brackish water plants. 



This habitat appears, on the whole, to be the most favor- 

 able of any that I have yet observed. The water, both of 

 Furnace Branch, and the smaller branch which flows into 

 Cinder Cove, is nearly always very clear. Usually its salt- 

 ness is but slightly perceptible to the taste, though, like the 

 Patapsco at Baltimore, ctenophores and barnacles are found 

 in it. The dam is located far enough inland so that its 

 constituent fragments are never disturbed by surf. The 

 branch flowing into the cove drains but a small, densely 

 wooded basin, so that the dam is never seriously molested 

 by freshets. The spot is well protected from cold winds 

 by adjacent banks and forests. The surrounding region 

 is but thinly inhabited, and the spot is rarely visited, 

 except by an occasional fisherman, huntsman, naturalists, 

 or stroller. The colonies are, therefore, left to grow and 

 multiply in peace. 



One feature of this habitat would seem to be unfavorable, 

 though the effects of such disadvantage, if present, are not 

 noticeable. As is well known, the tides of these estuaries 

 are'strongly influenced by the winds. During strong and 

 prolonged easterly winds I have seen the north bank of 



* They were fii'st observed among- the fragments of this dam by Drs. E. A. An- 

 drews and C. F. Hodge, of Johns Hopkins University, Nov. 19, 1887. Dr. Andrew- 

 states that his attention was first directed to this locality by Mr. Uhler. 



