488 



ANNELIDA. 



A horny plate may be developed on upper side of head. Anus usually 

 surrounded by a papillated funnel. Tentacles and branchiae absent. Noto- 

 podium small with simple or pinnate setae, absent posteriorly ; neuropodium 

 as transverse ridge with hooked setae, absent in anterior region. Inhabit long, 

 sandy tubes. Mitraria is a clymenid larva. Clymene Sav., head with plate ; 

 C. lumbricoides Qtf.; Pr axilla Mlmg.; Leiocephalus Qtf.; Maldane Gr., head 

 without plate ; Nicomache Mlmg. ; Axiothea Mlmg. ; Leiochone Gr. ; Petalo- 

 proctus Qtf. 



Fam. 3. Arenicolidae (Telethusidae). Prestomium small, without tentacles, 

 fused with peristomium. Peristomium without setae ; eversible buccal region 



covered with papillae, 

 without jaws. Notopodia 

 small, with a bundle of 

 simple setae ; neuropodia 

 with hooks in rows. 

 Branched gills on middle 

 segments. Posterior seg- 

 ments without parapodia 

 and gills. Burrow in 

 sand. Arenicola Leach ; 

 A. marina* L. (A. pis- 

 catorum Lam.). North 

 Sea and Mediterranean. 

 Lob- or lug-worm. Length, 

 5-6 inches (Naples speci- 

 mens smaller), colour, 

 brownish green. The bur- 

 rows are U-shaped, one 

 opening being marked by 

 a heap of vermicular, 

 sandy ejecta. Body 

 divided into three regions ; 

 an anterior thicker than 

 the rest, consisting of the 

 peristomium and 6 chaeti- 

 ferous segments ; a middle, 

 not so thick, of 13 chaeti- 

 ferous and branchiferous ; 

 a posterior much thinner 

 and devoid of setae and 

 branchiae, with segments 

 less clearly marked and 

 variable in number. In 

 the anterior and middle 

 region of the body there 



are 3 coelomic septa, the 1st behind the peristomium, the 2nd between the 

 2nd and 3rd setigerous segments, and the 3rd between the 3rd and 4th 

 setigerous segments. In the caudal regions the coelomic septa are segmental. 

 There are 6 pairs of nephridia in segments 4-9. 



FIG. 398. Anterior end of Arenicola opened from the dorsal 

 side, a anterior small chamber of the coelom ; 6, d, and / 

 first, second, and third septa ; c and e second and third 

 chambers ; g papillae of proboscis ; h oesophagus : i gut ; 

 fc gland ; I nerve cord ; TO setigerous sacs ; n nephridia ; 

 o anterior glands ; p heart ; q dorsal vessel ; r vesicles of 

 nephridia. (From Vogt and Yung.) 



* Vogt and Yung, PraUische Vcrgl. Anat., Bd. 1, 1888, p. 487. 



