COE: NEMEETEANS OF WEST AND NORTHWEST COASTS. 129 



A dorsal, longitudinal infolding of the integument can also 1)6 

 distinguished in the same region. This infolding will be described 

 below. 



Size. — Length 50-100 mm.; width about 2 ram. 



Proboscis sheath. — The rhynchodaeum is lined with columnar, 

 glandular epithelium (PI. 6, fig. 53) as far back as the attachment of 

 the proboscis, while the most anterior portion of the proboscis has 

 only flattened cells. These are soon replaced by columnar, glandu- 

 lar cells, as described below. 



The proboscis sheath has a layer of circular muscles which remains 

 rather thin throughout its length, except in the region of the great 

 thickening of the inner circular muscles of the body walls, and here 

 (PI. 7, fig. 50; PI. 8, fig. 57) the mixscular fibers of the proboscis 

 sheath increase correspondingly in strength. 



Internal to the circular muscles is a thin layer of longitudinal 

 muscles on which rests the thin epithelium of the rhynchocoel. Y?lv- 

 ther back this layer disappears, and the epithelium rests directly on 

 the circular muscles. Outside these latter occurs a second layer of 

 longitudinal fibers, much stronger than the inner layer, but not so 

 intimately connected with the proboscis sheath. Anteriorly they 

 are found only as two broad bands, one of which lies between the 

 circular muscles of the sheath and the alimentary canal (PI. 6, fig. 

 54), while the other lies above the sheath and separates its circular 

 muscles from the inner circular layer of the body walls. A little 

 farther back (PI. 7, figs. 55, 56) the layer completely surrounds the 

 circular muscles of the sheath, but remains thickest between the 

 sheath and the alimentary canal. 



Just at the end of the enormously thickened inner circular layer 

 of the body walls the circular muscles of the sheath fuse dorsally 

 with the few remaining fibers of the inner circular layer (PI. 8, fig. 

 58). At the same place the longitudinal muscles disap})ear both 

 dorsally and laterally, and become collected into a massive band 

 {Im}?) which lies between the sheath and the alimentary canal. This 

 band of muscles is very characteristic, and is similar to that found 

 in Carinella linearis and a few other species. It remains of great 

 strength well back into the intestinal region, and is entirely sepa- 

 rated from the longitudinal muscles of the body walls by the veiy 

 thin inner circular layer. It extends to the posterior end of the 

 proboscis sheath (PI. 8, fig. 58 ; PI. 9, fig. 59). 



