78 GUIDE TO LOCALITIES. 



in the mud of this beach. iV. palagica has been obtained from 

 the sand at about high-tide mark, and N. virens may be found also, 

 lower down on the beach. 



B. Estuarine faunas. Muddy brack and bottom, bridge-piles, 

 mud-flats and rocky shore. 



BEVERLY. 



Route.— By train, Boston and Maine road from North Union station 

 to Salem ; fare $.85. Take electrics (or bicycle, two miles) at Essex street 

 for Beverly bridge ; stop at Salem end of bridge. Obtain boat from Mr. 

 Powers, No. 2 Bridge street. Chief collecting grounds under the bridge, 

 and on the ledges in the estuary. The time of lowest tides should be 

 selected. 



In the mud about the boat-landing, Ilyanassa obsoleta is the com- 

 monest gastropod. It may be seen crawling by thousands in the 

 mud, and can be recognized easily by the comparatively smooth 

 spire and rather coarse aspect. With it occur large numbers of 

 Littorina littorea. Hermit crabs are very abundant in the mud 

 about the landing, but in this part of the estuary they seldom 

 bear Hydractinia. Gammarus ornatus may be found also, although 

 perhaps less commonly than on the more stony portions of our 

 shores. The best collecting is from the piles of the bridges, es- 

 pecially the road bridge. A number of distinct zones may be 

 recognized on the piles, each with its characteristic type of animal 

 life. The highest zone is occupied by the common barnacle, Ba- 

 lanus balanoides, which completely covers that portion of piles, 

 and in a measure serves as a protection to them. These animals 

 grow so closely crowded together that they are unable to assume 

 their normal form, and are obliged to increase chiefly in length. 

 One to two inches in length is not uncommon in this location, 

 with the diameter of the corona seldom exceeding half an inch. 

 Next below the barnacle zone we find the timbers, where 

 shaded, covered by our commonest campanularian hydroid, Cam- 

 panulariaflexuosa. This is flesh-colored, and often occurs in such 

 luxuriance as to cover the piles completely. When the tide is out 

 these hydroids hang down in brownish masses, often closely ad- 

 hering to the wood ; and under such circumstances they offer no 

 indication of the beauty which they will exhibit as soon as the re- 

 turning tide revives them. The species is quite hardy, and may 



