8 INVERTEBRATA OF MASSACHUSETTS. 



docks, and adheres by one side throughout nearly its whole length. 

 It is also found upon stones drawn up from the bottom of the 

 sea. It is well figured by Ellis, Corallines, pi. 34. 



The family Serpulea, Lam., have solid, calcareous tubes, more 

 or less coiled, much in the manner of serpents ; thus approach- 

 ing, in form, the regular shells. 



GENUS SPIR^RBIS, LAM. 

 Tube snail-like, flattened beneath and adhering. 



These are minute tubes, coiled up spirally, found adhering, in 

 large numbers, to marine plants, and sometimes shells, which are 

 thrown up from deep water. They are usually white, so as to 

 appear like dead and bleached shells. They adhere by their tips, 

 and, as they are presented to the eye, most of them appear 

 dextral ; but if we consider that we actually look at the base of 

 the shell, we perceive that they are in truth reversed. 



SPIRORBIS NAUTILOIDES, Lam. 

 State Coll., No. 262. Soc. Cab., No. 2312. 



Shell about one tenth of an inch in diameter, white and smooth, 

 or slightly wrinkled, consisting of three or four whorls, each in- 

 cluding the preceding one ; and, as each rises higher than the other, 

 they form a tunnel-shaped umbilicus, exhibiting a portion of each 

 volution ; the suture is indistinct, and the whorls seem con- 

 solidated ; the outer whorl is flattened out into a broad, spreading 

 base, where it is attached, thus increasing the diameter of the 

 shell at this part by nearly one half. Aperture circular. 



Found on sea-weed, shells, crabs, &c. It is the Serpula spi- 

 rorbis of Linnaeus. (FIGURE 3.) 



SPIRORBIS SPIRILLUM, Lam. 

 State Coll., No. 261. Soc. Cab., No. 2313. 



This shell is of about the same size as the preceding ; and is 

 distinguished from it by its more cylindrical structure, the much 

 greater distinctness of the whorls in the umbilical concavity, a more 



