NEMERTEA 



213 



3. OERSTEDIA Quatrefages. Body cylindrical, of similar 

 both ends, and rigid; 4 eyes forming a quadrangle; not over 

 long: 4 species; marine. 



0. dorsalis (Abildgaard) (Fig. 342). Body 10 mm. 

 long and very slender; color variable, mottled with green, 

 red, or brown : in shallow water on both the east and west 

 coast of North America and in Europe, very common on 

 piles and stones. 



form at 

 15 mm. 



ORDER 4. BDELLONEMERTEA. 



Fig. 342 



Oerstedia 



dorsalis, 



showing the 



front end of 



the body with 



the protruded 



proboscis 



(Verrill). 



Body short, flat, thick, and broad, with a large sucker 

 at the hinder end; intestine without diverticula and con- 

 voluted; proboscis without stylets, its opening coinciding 

 with the mouth and almost as long as the body; no eyes 



or cerebral organ: 1 genus 

 and 3 species, living commensally in the 

 branchial chamber of marine and fresh- 

 water mollusks; cosmopolitan. 



MALACOBDELLA Blainville. With the 

 characters of the family: 3 species. 



M. grossa (0. F. Miiller) (Fig. 343). 

 Hinder end of body broader than forward 

 end; male 3 cm. long and 8 mm. broad, 

 gray in color; female 26 mm. long and 13 



Fig. 343 Malacoldella grossa. mm. broad, yellowish or brownish in color : 

 A, entire worm (Verrill). 1, 



proboscis ; 2, mouth ; 3, intes- m Mya arenana, Venus, and other pe- 

 tine ; 4, sucker. B, section 



through the forward end (Biir- lecypods, on both Sides OI the north 

 ger). 1, mouth; 2, proboscis; 

 3, proboscis sheath. Atlantic. 



SUBPHYLUM 2. NEMATHELMINTHES.* 



Roundworms. Unsegmented, round worms, usually so elongated 

 and slender that they are called thread or hair worms, which are ento- 

 parasites in animals or plants or lead a free life in the water or in moist 

 earth. The body is not ciliated and is without paired appendages and 

 usually without external bristles, hairs, or suckers. With a very few 

 exceptions all are unisexual. 



The subphylum contains 3 classes. 



* See "The Determination of Generic Types and a List of Round Worms Genera 

 and Their Original and Type Species," by C. W. Stiles and A. Hassall, Bull. 79, Bur. 

 of An. Ind., Dept. of Ag., 1905. 



