26 INVERTEBRATA OF MASSACHUSETTS. 



Family TUBICOlArM, Lam. 



SJiells inclosed in, or attached to, a shelly tube. 

 Genus TEREDO, Lin- 



Valves equal, largely open above and below, placed at the larger 

 extremity of a tube open at both ends. 



Teredo nava'lis. 



Shell very widely gaping each side, and seated at the end of a 

 Jlexuous, calcareous tube. 



State Coll., No. 237. See. Cab., No. 2315. 



Teredo navalis, Lin. ; Syst.jYal., 12G7. Blainvili.e ; Malacol., pi. 81, f. 6. Sow- 

 erby; Genera. Brvg.; Encijc. Metk., pi. 167, i". I -5. 



This is the curious shell which is so remarkable for perforating 

 holes in timber, giving it a honey-comb appearance. These 

 holes are lined with their solid white tubes, at the bottom of which 

 the shell is found. The shell itself is small, the two valves 

 touching each other at only two points, and so much arched that 

 when in position they form a mere ring. 



It is occasionally found in ship-timber, especially where it has 

 been exposed to a tropical sea, and is familiarly known by the 

 name of the ship-tcorm. 



Family PHOLAdArIA, Lam. 



Shell without a tuhular sheath ; hinge aided by accessory valves, or very 

 widely gaping anteriorly. 



Genus PHOLAS, Lin. 



Shell transverse, gaping at botli sides ; hinge margin rolled out- 

 wards and toothless ; a rib-like tooth arises from the cavity of the 

 beaks, and shoots nearly across the shell. 



Shells of this genus are generally found in logs of wood, in 

 stones, or hard clay, which they have perforated ; and they have 

 one or more additional bony pieces on the back of the hinge. 



