UNIVALVES. SERPULA. 135 



SERPULA WormShell. 



Animal — a Terehella. ; Shell univalve^ tubulavt generalli/ 

 adhering to other substances; ojlen separated internally 

 hy divisions at uncertain distances. 



The genus Serpula contains forty-eight species; their 

 form (with few exceptions) is exceedingly irregular. They 

 are generally found in groups or clusters, adhering to 

 other substances, such as rocks, stones, roots of trees, sides 

 of ships, zoophites, sertulariae, fuci, shells, corals, &c. 

 They are invariably tubular, and present themselves some- 

 times isolated, either straight or twisted, but more fre- 

 quently in clusters, consisting of many hundred spiral and 

 twisted tubes, curiously interwoven with each other. 



Of the species which are isolated and spiral, may be 

 instanced the S. spirillum, S. spirorbis, and S. afra; which 

 have their whirls nearly contiguous, and resemble the 

 Hehces. 



Of the straight species, the S. protensa and S. poly- 

 thalamia are sufficient examples; the latter of which 

 most probably belongs to the genus Teredo: it is remark- 

 able for having its interior separated by imperforated 

 convex and concave divisions, making the shell appear 

 as if it consisted of numerous united tubes. The smaller 

 end of this shell is also peculiar for being terminated by 

 two distinct or separate small tubular pipes, which are 

 jointed in the same manner as the main stem from which 

 they spring ; the shell, in this state, resembles a two- 

 pronged fork. It is an inhabitant of the Mediterranean 

 and Indian seas, and is often found concealed under the 



