8. 



SiNISTRORSA. 



504 



ing : aperture orbicular, and invariably placed oppofite 

 the fun's apparent motion. Diameter not a line. 



Is not uncommon upon o\p,cr and other fiiells, and 

 upon algcE ; fometimes in company with 5. Spirorbis, 

 but from which it is readily diftinguiflied by the longitu- 

 dinal ridges, and by the contrary turn of the volutio ns 



Is found in fome parts of Kingsbridgc bay, on the 

 under fide of (late ftones, between high and low water- 

 mark, in fuch vaft abundance, that the furface of the 

 ftones is covered with them ; and in this fituation are un- 

 mixed with any other fpecies : poITibly the fub-faline 

 quality of the water fo far up this inlet, at ebb tides, is 

 not congenial to its congenera, for wc never found any 

 of the other Serpulcs fo far up. 



Serpula. Walk. Min. Shells, f. 13. l\. 



S. with a femi-pellucid, gloffy, white fiiell, with two- 

 or three reverfed volutions ufually placed lateral, but 

 fometimes coiled upon each other : it is fomewhat wrin- 

 kled tranfverfely, but has no longitudinal irregularities : 

 aperture orbicular. Diameter one line. 



The form of this fpecies is much like S. Spirillum, but 

 is at once diftinguiflied from it, by the aperture turning 

 the contrary way : it has the fame fub-pellucid appear- 

 ance 



