ALASKA NEMERTEANS 77 



the wall of one of the esophagal blood lacunas. Farther back the 

 branches unite into a single tubule on each side. Their main canal 

 continues backward for a considerable distance in the wall of a lateral 

 blood lacuna, and is without branches. At its posterior extremity the 

 efferent duct bends to the dorso-lateral surface of the body, as usual. 



The sexual products are fully mature in July. 



Habitat. This is a very active species. It was found in abundance 

 at Wrangell, Yakutat, Orca, and Virgin Bay. It inhabits the shore at 

 half tide and below, in muddy places and under stones. The small 

 size of the proboscis will distinguish it from related species. 



30. CEREBRATULUS LONGICEPS sp. nov. 

 pi. v, figs. 4, 5, 6, 7 . 



Body much flattened throughout its whole length ; anterior portion 

 remarkably narrow and slender, becoming wider posteriorly. Head 

 much narrower, more slender, and longer than in most species of the 

 genus, acutely pointed in front, much flattened dorso-ventrally, and with 

 the tip of the snout often slightly curved upward. A section through 

 the head is often concave both above and below, showing that the head 

 is thicker laterally than in the median line. The head is directly con- 

 tinuous with succeeding portions of the body. Frontal sense organs 

 very highly developed. 



Cephalic furrows very long, and remarkably deep and wide. An- 

 teriorly they do not reach quite to tip of snout. They are, conse- 

 quently, well separated from the proboscis pore, which is situated sub- 

 terminally. The mouth is situated as far back as the posterior end of 

 the cephalic furrows. 



From the narrow, pointed head the esophagal region gradually 

 widens as it passes backward, but it remains unusually flat throughout ; 

 the intestinal region is not sharply marked off from the esophagal 

 region, but widens gradually toward the posterior third of the body, 

 and narrows toward the posterior extremity. The intestinal region 

 is even flatter than the more anterior portion of the body. The caudal 

 cirrus was not observed. 



Proboscis. The proboscis sheath is reduced to a frail tubule in the 

 posterior third of the intestinal region. The proboscis is slender and 

 colorless ; it has the three muscular layers and the muscular crosses, 

 as usual in the genus. 



Color. Dorsal surface dark brownish-black or purplish, much paler 

 on tip of snout, and on borders of cephalic furrows. This paler border 

 is wider on the ventral than on the dorsal borders of the furrows. It 



