122 THREL, NORTHERN AND ARCTIC INVERTEBRATES. I. SIPUNCULIDS. 
Plate XI. 
Figs. 153—156. Onehnesoma squamatum KOREN and DANIELSSEN. West Coast of Norway. 
Fig. 153. Animal with the largest part of proboscis withdrawn. +. 
Figs. 154—155. Two other, fully extended, specimens. +. 
a. anal aperture. 
Fig. 156. Longitudinal section through the skin of the trumk. 130. 
ch. chitinous layer, showing a structure of exceedingly fine, crossing lines. — Im. longitudinal 
muscle layer. — och. outer incrusted layer. — p. papille in connection with glands. — se. 
irregularly formed scales of the outer incrusted layer. — tm. transverse muscle layer. 
Figs. 157—172. Onehnesoma Steenstrupii KOREN and DANIELSSEN. Skagerrack. 
Figs. 157—159. Three somewhat different forms, the smallest more rough than the larger ones. £. 
x. annular, narrow, slightly obscure, lines or bands. 
Fig. 160. The segmental organ with close-lying fixing muscles. 25. 
» 161. Front view of the mouth with its disk, devoid of tentacles. 0. 
» 162. Side view of the anterior portion of the proboscis from another animal, part of the 
alimentary canal having been ejected through the anus. 30. 
m. mouth. — rm. retractor muscles. — td. tentacular fold of the oral disk. 
» 163. Side view of the proboscis of another specimen. 50. 
a. anus on its papilla. — m. mouth. — ne. nerve cord. — oe. oesophagus. — r. rectum. — 
rm. retractor muscle. — td. tentacular fold of the oral disk. 
» 164. Front view of the former. 9. 
» 165. View of the foremost, retracted, part of the proboscis from another specimen. 2. 
a. anus. — m. mouth. — oe. oesophagus. — r,. rectum. — rm. retractor muscle. 
» 166. WNurface-view of a piece of skin of the proboscis. 130. 
» 167. The same as before. 330. 
» 168. MNurface-view of a piece of skin from the proboscis, presenting an obscure annular line, 
glands and corpuscles. 350. 
x. the obscure annular line. 
» 169. Side view of the former. 320. 
x, the obscure annular line. 
» 170. Side view of the skin from the anterior part of the trunk. 130. 
p. papilla with gland. — sc. incrusted, more or less irregular, elevations. 
» 171. BSurface-view of the skin from the anterior part of the trunk. Letters as before. 130. 
» 172. BSurface-view of the skin from about the middle of the trunk. 130. 
p. papilla with gland. — sc. incrusted, irregular, scale-like, elevations of the skin. 
