COE: NEMERTEANS OF WEST AND NORTHWEST COASTS. 153 



are actually due to the states of contraction of the parts. Their 

 number apparently varies from 6 to 10 in different individuals. 



Reprodiictwe organs. — Ovaries and spermaries develop between 

 the intestinal lobes and are mature in August, both on the California 

 coast and in Puget Sound. 



Habitat. — In sand and in hard blue clay between tides, and on 

 piles of wharf, in Strait of Juan de Fuca and in Puget Sound, 

 (Griffin, '98) ; between tides, Vancouver Island, collected by Shearer 

 (Coe, :01); common in sand between tides in San Pedro Harbor, 

 ■California ; also found in sand in San Diego Harbor, California, but 

 not in abundance. 



Cephalothrix Oersted. 

 Entwurf der Plattwilrmer, Kopenhagen, 1844. 



This genus includes very long, slender, filiform species which 

 show a tendency to coil in a close spiral. Brain situated well 

 behind tip of snout ; mouth several times as far posteiiorly. Head 

 sharply pointed in extension ; proboscis pore on ventral side a lit- 

 tle back of its extremity. Inner circular muscular layer very much 

 reduced, or (commonly) entirely absent, the body musculature con- 

 sisting of a thin outer circular muscular layer and a strong inner 

 longitudinal layer ; lateral nerves situated in the longitudinal mus- 

 cular layer ; cerebral sense organs and cephalic furrows wanting. 

 These worms resemble in external appearance some of the slender 

 nematodes. 



A single species, which is also found in European waters and on 

 the east coast of North America, occurs abundantly on the Pacific 

 coast of Alaska. Three other species of the genus have been 

 described from Europe and a fifth occurs in the Indian Ocean at 

 the Maldive Islands (Punnett, •.OV'). 



10. Cephalothrix linearis (Rathke) Oersted. 



Planaria linearis Rathke, Skrivter af Naturhist. Selsk. Kjoben- 

 havn, 5, p. 84, 1799. 



Cephalothrix linearis Oersted, Entwurf der Plattwiirmei*, p. 82, 

 Kopenhagen, 1844. Coe, Proc. Wash. Acad. Sci., 3, p. 19, 

 1901 ; Harriman Alaska Expedition, 11, p. 19, 1904. 



