216 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 15 



known before the end of the nineteenth century. The earliest American 

 species were described by Verrill (1873 to 1900), Webster (1879 to 

 1884) and Kinberg (1867). Others have been added in more recent 

 times. 



Family Characteristics 



Typically the body is long, slender and often appears ragged in its 

 posterior part because of the presence of dorsally directed parapodia and 

 branchiae. Color in life is generally pale orange or yellowish red with 

 bright red branchiae (due to the color of the red blood). The body 

 consists of a shorter thorax and a much longer abdomen. These parts are 

 weakly separable (in the PROTOARICIINAE, new subfamily) to 

 more or less abruptly different (in the ORBINIINAE, new subfamily, 

 especially in the genera Orbinia and Phylo). The change is most notice- 

 able in the narrowing of the body in the abdomen and in the difference 

 in position and structure of parapodial lobes and setal fascicles. In the 

 thorax the neuropodia have short, transversely prolonged fleshy ridges; 

 in the abdomen they are longer and slenderer to cylindical in shape. 



The prostomium is an inconspicuous lobe, truncate or semicircular 

 or elongated conical ; it has no appendages but the everted nuchal organs 

 located at the posterior sides have sometimes been mistaken for short 

 antennae. Prostomial eyes are present, especially in juvenile stages, or 

 absent or so deeply embedded as to be unseen in older and preserved 

 individuals. The nuchal organs are ciliated, slitlike invaginations located 

 at the posterior ectal margins of the prostomium. The prostomium may 

 alter its shape with age or method of fixation. In juvenile stages it is 

 more or less semicircular or rounded in front ; in later stages it may be 

 long and pointed or conical or abruptly truncate in front. 



The proboscis or anterior end of the alimentary tract is unarmed. In 

 the ORBINIINAE it is an eversible, epithelial, simple or multilobed 

 pouch secondarily derived from a portion of the ventral side of the 

 anterior end of the alimentary tract. In adult stages of some species it is 

 voluminous and much branched dendritically ; when everted it may 

 conceal the prostomium and the ventral part of the first few segments. 

 In the PROTOARICIINAE, as in Protoaricia and perhaps also in 

 Proscoloplos and Orbiniella, it is muscular and primarily derived from 

 the anterior end of the alimentary tract and of limited proportions 

 (Eisig, 1914, p. 162 as Theostoma). 



In the ORBINIINAE the first segment or peristomium is a smooth, 

 sometimes partly biannulated ring without parapodia; in the PRO- 

 TOARICIINAE the first and second segments are without parapodia; 



