232 W. C. ALLEE. 



Gansett; 83 and 118 are from Blind Gutter Flats. The others 

 are from NW. Gutter Flats. 



One open space in the eel grass, similar to those occurring 

 scattered over the flats, except that it is larger and occurs near 

 the margin, is to be found at NW. Gutter where a gravel spit 

 extends from Uncatena Island partially across the creek leading 

 to Hadley Harbor. On the Hadley Harbor side of the spit is a 

 space covering some 2-3 square rods close up in the angle made 

 by the gravel with the shore. The almost bottomless muck is 

 covered over by a thick layer of old eel grass which acts as a 

 very effective matting over the soft ooze below. Such eel grass 

 is very resistant and decays slowly. The main tidal current 

 flows past the edge of this eddy and thus prevents conditions 

 from becoming as extreme as they would otherwise. 



In addition to the numerous mud snails (Nassa obsoleta), one 

 may find here : a few hermit crabs (P. longicarpus) carrying Hy- 

 dractinia and the snail, Crepidula convexa. In places the common 

 Littorina litorea, almost equals the mud snails in numbers and in 

 other nearby regions only the latter are found. Some Libinia 

 dubia are also on the surface while under the matting one finds 

 nothing save a few Scoloplos fragilis. 



The analytical data collected from this locality is shown in the 

 latter part of Table X, commencing with collection No. 7. In 

 many respects the conditions in this particular location resemble 

 those of the Thyone association and seem to present a transition 

 stage between the two associations. This will be discussed in 

 detail in the last section. 



e. Marginal Muck {Thyone) Association. — Thyone occurs in the 

 preceding association as well as here, but since they are easily 

 the most conspicuous animals in this environment and there are 

 at least as many of them here as among the eel grass, and they 

 may be absent in typical 5. acutus conditions, the name is 

 entirely appropriate. 



The marginal muck association inhabits the region between the 

 edge of the eel grass and low tide and overlaps both the preceding 

 and the following associations. The eel grass on muddy shores 

 usually begins to grow where the water is from one to two feet 

 deep at low tide. This leaves a space from one to two rods wide 

 on the inner side of Northwest and Blind Gutter Flats, bare of 



