490 ANNELIDA. 



Branch B. CKYPTOCEPHALA. 



Prestomium more or less hidden by the peristomium which grows 

 forward. The tentacles are reduced, but the palps are greatly developed 

 and subdivided, forming the crown of gills. The body is distinguish- 

 able into two regions the thorax and abdomen characterized by the 

 form and arrangement of the setae, and by cei^tain internal differences.. 



Sub-order 1. SABELLIFORMIA. 



Prestomium entirely hidden by the forward extension of the 

 peristomium ; tentacles very small, being often represented by small 

 knobs of sense-cells; palps large and vascular, acting as respiratory 

 and sensory organs. Peristomium without cirri or setae; it is 

 usually raised into a projecting collar used in fashioning the lip of 

 the tube. The parapodia are small; cirri are absent except in the 

 Serpulidae. The setae are of two kinds hair-like and uncini; by 

 their arrangement the body is divided into a thorax, typically of 

 nine segments, and into an abdomen; in the thorax the hair setae 

 are dorsal, in the abdomen ventral. The buccal region is not 

 eversible; there is no pharynx. Septa absent in thorax, present 

 in abdomen. There are two large nephridia in the thorax, opening 

 by a median dorsal pore just above the brain ; while the nephridia 

 of the abdomen are small funnels which act as generative ducts. 

 Tubicolous; gland-shields are present on the thoracic segments. 

 Some genera are hermaphrodite. 



Fam. 1. Sabellidae * (including Eriographidae and Amphicorinidae). Tube 

 formed of mucin of variable consistence and more or less transparent, covered or 

 not with mud, sand, or pieces of shells. Without thoracic membrane and 

 operculum. Branchial filaments usually arise from a semicircular base. The 

 ventral gland-shields are continued on to the abdomen. A median ciliated 

 groove, usually situated on the ventral surface (it sometimes bends to one side 

 on reaching the thorax, and may extend forwards on the dorsal surface to the 

 head), starts from the anus and conducts the faecal matters to the opening of 

 the tube. The species are highly variable : the individuals of the same species 

 often vary in the following features ; colour, number of branchiae, form of 

 collar, number of thoracic segments, number and position of eyes and otocysts. 



Spirographis Viv., the basal lamella of the gill filaments describes several 

 turns in spiral. The branchiae of the two sides are of unequal size ; Sp. 

 spallanzanii Viv., Naples ; Bispira Kr. Like preceding, except the two 

 branchiae are equal. Sabdla L., gill-filaments arise from a semicircular base, gills 

 equal, two filamentous dorsally-placed lip-processes (found in other Sabellids : 

 they are not tentacles) ; S. pavonina Sav. ; Potamilla Mgr. ; Hypsieomus Gr. ;. 

 Potamis Ehlers ; Branchiomma Roll., with a compound eye close to the tip 



* St. Joseph, Ann. Sci. Nat. (7), 17, 1894, p. 248. 



