207 



whirli pl<i>' Ml inipiirtaiil a rok- in the- fCdiKiiiiy (if most marine- <irt;anisnis. Hence the 

 usually recognized zoogeographic lactors are (il relatix (.■!>■ niinor ini|)(irtance in limiting 

 the distribution of this species. 



This point is borne out by the fact that Liivnoria li'j,nonti)>, an organism belonging 

 to an entirt'ly difterent grouji, but likewise specialized tor boring in wood, has a 

 remarkabh' cosmopolitan distribution. 



The sudden and catastrojihic activity of this |)arlicular Teredo in San I'rancisco 

 Ba\' woidd appear to be proof positixe that it has been introduced from some other 

 locality. The Pacific Coast has been ransacked for decades by conchologists, but 

 this organism has never been found until recent years. Its behavior since its discovery 

 in .San Francisco Bay in 1914 is of such a nature that it is highly improbable that it 

 could ha\'e been present in earlier years and escaped notice. Untreated piling at 

 l^ort Costa dri\'en prior to 1870, so far as can be determined was untouched In- Teredo 

 prior to the recent outbreak, although several periods of low rainfall had inler\ened 

 which would have been favorable to such an outbreak had the organisms been present. 



Our specimens from San Francisco Ba>' compare closely with specimens of 7". 

 navalis which we have received from various localities in Europe and along the Atlantic 

 Coast of North America. A detailed study of a large series of shells and pallets (Miller, 

 1922 and 192,^) has brought out the fact that the range of the variations produced by 

 different conditions in different portions of the Bay, and e\'en by the different condi- 

 tions obtaining at the top and bottom of the same pile, is of greater magnitude than 

 the differences that have been stated to exist between the type of T. navalis and the 

 San P'rancisco Bay form. Specimens from San Francisco Bay which we have sent to 

 Paris have been identified by Dr. F. Lamy of the Museum d'Histoire Naturelle as 

 T. navalis, and Dr. W. T. Caiman of the British Museum writes that our figures are 

 undoubtedly of that species. 



It appears therefore that there are sound biological reasons for belie\'ing that 

 the species we have under consideration is true Teredo navalis, which has lately been 

 introduced here from some other area of distribution. 



