xii CAPITELLIFORMIA SCOLECIFORMIA 331 



inside and out. These tubes can be carried about by the worm, 

 but may be found projecting from the sand at very low tides. 

 P. belgica Pall, forms a straight tube, whilst in P. auricoma 

 MulL the tube is larger and slightly curved. The former species 

 appears to be confined to the North Sea ; the latter occurs in 

 deeper water, and is also present in the Mediterranean. 



Sub-Order 4. Capitelliformia. 



FAM. Capitellidae. 1 Capitella capitata v. Ben. occurs pretty 

 frequently in the sand under stones near low tide-mark. It is a 

 red worm, about l^- to 2 inches long, greatly resembling a Tubi- 

 ficid Oligochaete. It may readily be distinguished from other 

 Polychaeta by the strong genital chaetae in the male, which 

 replace the notopodial chaetae of segments 8 and 9 ; those in the 

 former segment are pointed backwards, and in the latter forwards. 

 There is but a single pair of generative ducts in either sex in 

 the eighth segment. North Sea, Mediterranean. 



Notomastus latericeus Sars is a longer worm, living in shallow 

 water, off our coast and in the Mediterranean. The anterior 

 twelve segments are wider than the rest of the body. The 

 notopodial chaetae of the anterior segments of the hind body 

 form a ring. Dasylranchus caducus Gr., which occurs in the 

 Mediterranean, but not on our coast, reaches a length of 2 or 3 

 feet. It has gills on the hinder segments above the neuropodia. 

 Mastobranchus Eis. is found in the Mediterranean. 



Sub-Order 5. Scoleciformia. 



FAM. 1. Opheliidae. Comparatively short, rather ugly worms 

 of a pearly colour, no prostomial processes : parapodia obscure. 

 The family is represented in British waters by four species, 

 occurring in shallow water. 



Ammotrypane aulogaster Eathke, is about 2 inches long; 

 the nearly cylindrical body has a ridge running along each side 

 below the chaetae. The conical prostomiuin is tipped with" a 

 small knob, and carries at each side a ciliated pit (Fig. 144, 

 p. 273). Every segment, except the first chaetigerous, is pro- 

 vided with a filamentous gill (dorsal cirrus). The segmentation 

 1 Eisig, "Die Capitelliden, " Fauna u. Flora 0. v. Neapcl, Monogr. xvi. 1887. 



