MONOGRAPH OF AMERICAN SHIPWORMS. 3 



turbidity, food, etc., as the determining environmental factors which 

 shift their relative proportions in the sea as on the land, and thus 

 afford the differences that go to make up the environment of the 

 different zoogeographic areas. 



Mollusks Avhen transplanted from one area to another may per- 

 sist through the natural life of the individual, but may find it im- 

 possible to reproduce, the environmental adjustment in larval 

 bivalves being particularly sensitive, as emphasized by the oyster. 



I have dealt with greater detail upon this topic because some 

 naturalists have conceived a wider distribution to species of ship- 

 worms than we usually accord to species of other groups, though I 

 am sure that had they possessed adequate material for study, they 

 would have voiced another opinion. 



The finest piece of life history work on shipworms so far done 

 is that by Prof. Charles P. Sigerfoos, in his Natural History, Or- 

 ganization, and Late Development of the Teredinidae, or Ship- 

 Worms.^ It is particularly noteworthy that Sigerfoos carefully 

 established the identitv of the material used in his studies, remov 

 ing the last question of doubt by placing a representative series oi 

 specimens in the United States National Museum, where they will 

 typify his researches, regardless of nomenclatorial vicissitudes that 

 may befall the names he used. His studies were based upon mate- 

 rial collected at the United States Bureau of Fisheries Station at 

 Beaufort, North Carolina. The species whose life history he almost 

 completely worked out is " Xylotrya govldi^^'' now Bankia {Baivki- 

 eJla) gouldi Bartsch, which he traced from the Qgg through the 

 early lamellibranch veliger larval stage, and later from the time 

 of its settling stage to the adult worm. The only gap left in the 

 life history of Bankia {Bankiella) gouldi is that which trans- 

 pires between the veliger and the newly attached larva. He also 

 traced the early embryologic history of '-''Teredo dilatata^'' which 

 I have renamed Teredo {Psiloteredo) sigerfoosi in the present 

 treatise. 



A few points of general interest may be added to this introduction 

 before undertaking the systematic treatment, the main object of the 

 present study. 



Why and how does the shipworm make the burrow that renders 

 him obnoxious to man? As to why we may say that he needs it for 

 the protection of his long, soft body. Most bivalve mollusks have 

 a shell into which they may withdraw for protection in case of danger™ 

 Shipworms and the mollusks of several other families, however, have 

 a much reduced shell that covers only a part of the body in the adult 

 state (pi. 1, fig. 1, and pi. 2). In shipworms, in fact, the primary 



' Bull. U. S. Bur. Fish., vol. 27, pp. 191-231, pis. 7 to 21. 



