NEMERTEA 



207 



C. tremaphoros C. B. Thompson. Bod}' 12 era. long, 3 mm. thick, 

 butf in color; head white, flattened, ronnded in front: Woods Hole. 



Order 2. HETERONEMERTEA. (Sciiizonemertea.) 



Body often very long; month behind brain; proboscis without 

 stylets; cerebral organ present; a caudal cirrus sometimes present; body 

 wall contains three muscle layers of which the outer is longitudinal and 

 between which and the circular muscles are the lateral nerves; cutis well 

 developed : 2 families and over 170 species. 



Family LINEIDAE. 

 Body usually very long, but in some species relatively short and 

 thick; a pair of conspicuous lateral sensory grooves usually on the head; 

 3 muscle layers in proboscis; the outer one being longitudinal; cephalic 

 gland small and slender: 10 genera and about 150 species. 



Key to the genera of Lineidae here described: 

 Ci Caudal cirrus not present. 



6i Lateral sensory grooves wanting 1. Parapolia 



62 Lateral sensory grooves present 2. Lineus 



a. Caudal cirrus present. 



61 Lateral sensory grooves wanting 3. Zygeupolia 



62 Lateral sensory grooves present. 



Ci Lateral body edges not thin ; animals cannot swim 4. Micruba 



Cz Lateral body edges very thin ; animals swim 5. Cerebratulus 



1. Parapolia Coe. Body cylindrical anteriorly, flattened poste- 

 riorly ; head not set off from body ; without sensory grooves on the head ; 

 eyes not present; cerebral organs a pair of flat 



elevations: 1 species. 



P. aurantiaca Coe. Color orange; length 25 

 cm.; width 10 mm.; thickness 4 mm.: Vineyard 

 Sound, at low-water mark. 



2. LiNEXTS Sowerby. Body extremely long and 

 filiform or tape-like and very contractile; head 

 somewhat wider and tapering to a point; usually 

 with eyes : about 50 species ; cosmopolitan ; animals 

 cannot swim, and usually twist themselves into an 

 irregular mass. 



L. ruber (0. F. Miiller) (L. gesserensis 0. F. 

 Mill.; L. viridis Johnston) (Fig. 335). Body 

 cylindrical ; color very variable, being green, brown, 

 or reddish ; a single row of 4 to 8 eyes on each side 

 of head ; 20 cm. or more ; width 6 mm. : common under stones in shallow 

 water from Long Island to Greenland; Alaska; Europe; breeds in June 

 at Woods Hole. 



Fig. .3.35 

 Lineus ruber (Verrill). 

 A, whole worm ; B, 

 head, showing lateral 

 groove. 



