THE NAUTILUS. 113 



Alectrion trivittata (Say) common. 

 Eupleura caudata (Say) few. 

 Urosalpinx cinerea (Say) occasional. 



The sod-bank or Modiolus demissus association was to be 

 found on any clay or hard-mud bank exposed between tides. 

 This association consists principally of Modiolus demissus pli- 

 catulus packed tight one against the other or separated by 

 Mytilus edulis packed just as closely, over both of which crawl 

 Litorina littorea and L. rudis. Modiolus demissus demissus is found 

 very thinly scattered among the individuals of the northern 

 form. That the southern variety was once the predominant 

 form over this area is evident from the fact that the sod banks 

 on which plicatuliis is now living contain the dead valves of the 

 southern form exclusively, in large numbers and buried to a 

 depth of 8 or 10 inches below the surface in company with My a 

 arenaria. I do not think the two forms interbreed. 



Half a mile southeast of the bay where there is a stone jetty 

 running out into water four to five feet deep at low tide, the 

 rocks and bottom were searched but with very discouraging re- 

 sults. The water all along this section of the island is heavily 

 laden with fine mud from the red dirt characteristic of that part 

 of the island. This we believe to be the reason for the scarcity 

 of mollusca along the beaches southeastward. A shattered but 

 uneroded and still united pair of valves of Modiolus modiolus 

 (Linne) were found at Seaside Beach. 



Our survey of the island showed the north and northeast 

 shore of the island to be rocky and built over by commercial 

 interests. From Fort Wadsworth to Prince's Bay (the south- 

 east cost) there are sandy beaches interrupted by sod-banks. 

 As one progresses southeastward these beaches become more 

 and more rocky to Prince's Bay, from which point and around 

 the southern end of the island the shore is characteristically 

 rocky. The remaining (western) coast line is lost in a maze of 

 salt marsh. Thus there are but two places along the southeast 

 coast of Staten Island where Mollusca are of special interest, 

 namely, the sand flats between South and Midland Beaches and 

 the complex about the base of the Great Kills Bay spit. The 

 southern end of the island was not studied. 



