10 INVERTEBRATA OF MASSACHUSETTS. 



Serpula vermicula'ris. Lin., &c. 



State Coll., No. 260. Soc. Cab., No. 851. 



Shell cylindric, the tube gradually enlarging, white, somewhat' 

 wrinkled circularly, usually adhering throughout its whole length, 

 but observing no particular mode of convolution ; when arrived 

 at a large size, the aperture is of the magnitude of a goose's 

 quill. 



We may now proceed to describe the testaceous mollusca of 

 this State, in their natural order, so far as that order is yet de- 

 termined. 



They may be arranged, in the first place, under three grand di- 

 visions, based principally upon their most conspicuous external 

 organs, those which are employed in progression or in procuring 

 their food. 



A. Tentacular branchiae fringed and coiled, used for prehension ; 

 shells multivalve, Cirri'pedes, Lam. 



B. Inhabiting bivalve shells, Conchi'fera,* Lam. 



C. Having a foot beneath them adapted to creeping ; shells mostly 

 univalve, Gastero'poda, Cuv. 



It will not be necessary to enter into an exposition of all the 

 families and further sub-divisions which may, or might, have been 

 instituted. The object is to render the matter as available as 

 possible to beginners in science, or to the general reader. 



* The more comprehensive and more approved term Acehhala is here avoided, 

 in order to exchide the Ascidlens of Lamarck, which are true headless mollusks, 

 but witiiout shells. 



