170 MARINE INVERTEBRATES 



GENUS Cerebratulus 

 C* anffulatus. Olive-green, with light dorsal stripe. 



GENUS Cosmocephala 



C. ochracea. Two to three inches long when extended -, gray or 

 yellowish-white, and mottled by the internal organs showing through 

 the translucent body ; line of lighter color down the back ; anterior end 

 often orange-colored. It is common near low-water mark under stones 

 and in the dead tubes of Serpula. 



GENUS Polina 



P. glutinosa. One to two inches long ; color orange or light yellow, 

 with a faint line of deeper color down the center of the dorsal surface ; 

 very slimy; eyes numerous, in oblique lines on the head. Found in 

 tide-pools on algae. 



PHYLUM NEMATHELMINTHES 



ROUNDWORMS 



The worms of this phylum have the general name of round- 

 worms, which distinguishes them from the flatworms of the pre- 

 ceding division and from the segmented worms of the Annulata. 

 The body is elongated, cylindrical, smooth, and pointed at both 

 ends. With few exceptions, they are parasitic. 



A few of the nematode species are free, living under stones 

 and among seaweeds at about low-water mark. 



CLASS NEMATODA 







GENUS Pontonema 



P. marinum. Slender, white, smooth, active, cylindrical; con- 

 stantly coiling and uncoiling itself. 



PHYLUM ANNULATA 



SEGMENTED WORMS 



The name of this phylum expresses the principal characteristic 

 of the group of worms which have elongated bodies composed 

 of series of short parts, or ring-like divisions. Each one of these 

 segments contains a separate and similar set of internal organs. 



