ZOOLOGY : MARINE INVERTEBRATES. 



75 



numbers, and may be dug also at low water a little below 

 the surface of the sand. Leptosynapta girardii may be dug on 

 the banks of the Saugus river at the northern end of the beach, 

 as well as in front of the Point of Pines hotel. Balanoglossus 

 may be obtained by digging near low-water mark on the beach. 

 It is most abundant opposite Oak island, and from there to the 

 Point of Pines. After northeast storms it frequently is cast up 

 in numbers on the beach. 



The two sponges common on this beacii are CUona sulphurea and 

 Chalina ocidata. The former is represented chiefly by its borings 



Ecftinararhnitis ptirma, 

 (After Fewkes, by courtesy of the Essex Institute.) 



in the shells, and the latter by dried specimens on the upper part 

 of the beach. 



A number of hydroids and bryozoa are cast up attached to 

 various seaweeds. Among tlie former Obelia tjeniculata may be 

 found commonly attached to the fronds of the Laminaria, although 

 specimens in the living condition seldom can be obtained. 



Sertularia pumila usually is found attached to the rockweed 

 Fucus and Ascophyllum, and Sertidaria argentea can be found also 



