— 49 — 



nearly the same size throughout their length, a peculiarity whieli bears 

 directly upon its habits. The um])os are central in position, the 

 siphons separate and long. 



Habitat and habits — Tafjclus is a form inhabiting quiet bays, where 

 it is found in mud or muddy sand. Unlike most clams it digs a 

 smooth lined permanent burrow which its elongated cylindrical shell 

 fits snugly and in which it moves readily up and down. A good idea 

 of the burrow may be gained from figure 22. It extends vertically 

 downward some 15 or 16 inches, thus reaching loose w^atery mud or 

 sand. When at the top of the burrow the jackknife clam is about 

 its own length from the surface, and the siphons reach the overlaying 

 water through two small holes ending an inch and a half or two inches 



Fig. 2:^. The jaokknife cImih < / The 



one on the right i.s at tlie to]i ■>! i. : - . that 



on the left at the l)Ott(>ni. Note tlie two 



separate siplion holes at the top of the left 

 burrow. 



apart. If disturbed the clam pulls in its siplions and by means of its 

 powerful foot rapidly retreats to the bottom of its burrow. If still 

 followed it will commence to dig into the softer underlying mud or 

 sand, though here its progress is not so rapid. 



Use — The jackknife clam is said to have a fair flavor and is in 

 many places very abundant, so that it may be considered a potentially 

 valuable species. Its use as food, however, was not observed in any of 

 the localities visited. At False Bay it was sold locally for bait by 

 small boys who collected them in an ingenious fashion. A stout wire 

 about the size of a pencil armed with an arrowhead made from an old 

 tile was thrust down the burrow as located by the siphon holes and 



4—6453 



