CAPITELLIDAE. 465 



unarmed, used in boring. Anus terminal, usually surrounded by a large rim 

 bearing papillae. There is a straight oesophagus followed by a stomach, below 

 which is the accessory gut ("nebendarm") opening into it at both ends and 

 supposed to be respiratory in function. 



With the exception of Eisigella onanaryensis all the known capitellids are 

 marine. They occur in sand and mud, in the detritus of Algae, or in the fissures 

 of rocks, for the most part in tubes which they construct. They live upon 

 minute organisms, such as diatoms, foraminifers, and radiolarians, and upon the 

 organic fragments occurring in the sand or mud in which they live. 



Key to Genera. 



a. Thorax with exclusively capillary setae. 

 b. Abdomen with crochets exclusively, 

 c. Branchiae present. 



d. With twelve thoracic somites; branchiae single filaments Notomasius Sars. 



e. Genital ducts and pores absent or rudimentary Subgen. Clistomastus Eisig. 



ee. Genital ducts and pores well developed Notomasius sens. str. 



dd. Fourteeia thoracic somites; branchiae of two or more tufted filaments. 



Dasybranchus Grube. 

 cc. Branchiae none. 



d. Eleven setigerous thoracic somites, no macroscopic distinction otherwise between thorax 



and abdomen Capitellethus, nom. nov. 



dd. Thorax of twelve or thirteen setigerous somites. 



e. Twelve setigerous thoracic somites Eisigella Gravier. 



ee. Thirteen setigerous thoracic somites. 



/. An anal funnel supported by acicula or spines; with two anal cirri. 



Scyphoproclus Gravier. 



ff. With no spine-supported anal funnel Leiochrides Augencr. 



bb. Abdomen with capillary setae in addition to the crochets. 



c. No branchiae; first abdominal somite with capillary setae Leiochrus Ehlers. 



cc. Branchiae present. » 



d. With twelve thoracic somites Mastobranchus Eisig. 



dd. Eighteen (or seventeen) thoracic somites Eunotomastus Mcintosh. 



aa. Thorax with crochets in addition to the capillary setae. 

 b. With but nine or ten thoracic somites; no branchiae. 



c. Nine distinct thoracic somites (morphologically ten, but the first fused with the prostomium) ; 

 1 to 6 with capillary setae, 8 and 9 crochets (and 7 often with both). 



d. Special copulatory setae in the males only Capitella Blainville. 



dd. Copulatory setae occurring in both sexes. 



e. Copulatory apparatus alike in both sexes (one copulatory seta in each notopodium of eighth 



and ninth somites) Capilellides Mesnil. 



ee. Copulatory apparatus strongly differing in the two sexes (copulatory setae forming a 

 single group on eighth and ninth somites in male, and in less developed form on 



seventh and eighth in female) Isoma.'itus Gravier. 



cc. With ten thoracic somites (2 to 4 or 5 with capillary setae, and 5 or 6 to 10 with crochets). 



Capitomaslus Eisig. 

 bh. With twelve or more thoracic somites. 



c. With twelve or thirteen thoracic somites; first three or four with capillary setae only. 



d. Twelve thoracic somites Helcromastm Eisig. 



dd. Thirteen thoracic somites Hcleromasiidcs Augcner. 



cc. Eighteen thoracic somites; first fourteen with capillary setae only. .. ./^sew<ioca/;i<e//a Fauvel. 



