III. AXXELIDA; CH.ETOPODA 



organic tubes in -ivhich foreign matter may be incorporated or which may be 

 calcified. The worms project their anterior segments from the tubes. The 

 Errantia often burrow, but from time to time swim about preying on other ani- 

 mals. Correlated with habits are differences in structure. In the Errantia the 

 head and trunk are not very different; the anterior part of the alimentary tract 

 can be protruded as a proboscis, and, corresponding to their predaceous habits, 

 is often armed with strong jaws (fig. 260). The Sedentaria have no such 

 teeth, but there is a greater difference between anterior and posterior somites. 

 In the latter the parapodia are weakly developed, and this part resembles the 

 Oligochfctes in appearance. The head and beginning of the trunk (lliorax) are 

 richly pro\'ided with gills and tentacles for respiration and taking food (fig. 261). 



Fig. 263. — New England Annelids ffrom Emerton and Verrill). ,1, male Autolytus; 

 B, Sternaspis fossor; C, Cistenldes gouldii; D, Clymene torquata. 



Sub Order I. ERRANTIA. Predaceous annelids with strongly armed 

 pharynx. The EuxiciDiE, mostly represented on our shores by small species, 

 contains some species a yard in length. Diopalra* Nothria* Alciopid.^, 

 transparent, pelagic, with large, highly developed eyes (fig. 84). The Syllid^ 

 usually have three long tentacles; Autolylus'' (fig. 263), M yrianida* (p. 275). 

 The POLYNOID.S;* {Lepidonotus* Polynoe* (fig. 262), are bottom forms with 

 elytra. Nereid.^;; Nereis virens,^- clam worm of all northern seas. 



Sub Order II. SEDENTARIA (Tubicola). These cannot wander, but 

 live in tubes. Sabellid.e, tube is membranous and there is a crown of gills; 

 Alyxicola,'* Chonc* Manyunkia* Serpulid^, tube calcified and closed by an 



