304 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



83. Amphinemertes caeca (Coe), 1901 



Tetrastemma caecum Coe, 1901, 1904, 1905, 1905a. 



Habitat. Dredged with tunicates at a depth of about 5 m; presumably 

 parasitic or commensal in tunicates. 



Distribution. At present known only from near Kodiak Island, 

 Alaska. 



Genus TETRASTEMMA Ehrenberg 



Nine species belonging to this genus have been found on the North 

 Pacific coast. Only one of these is known to occur in other parts of the 

 world. 



Key to Species 

 1. With 4 well-developed ocelli 2 



1. With 4 fragmented ocelli aberrans 



2. Dorsal surface with conspicuous brown stripes or rectangular 

 markings or both 3 



2. Dorsal surface without brown stripes or rectangular markings 6 



3. Dorsal surface with 2, 4, or 6 brown stripes 4 



3. Dorsal surface with brown rectangular markings and stripes 

 reticulatum 



4. Flesh color, creamy, or grayish, with 2 brown longitudinal 

 stripes on dorsal surface T. bilineatum 



4. Whitish, with 4 or 6 brown longitudinal stripes 5 



5. With 4 brown stripes, of which 2 lie on dorsal surface and 2 



on lateral margins of body quadrilineatum 



5. With 6 brown stripes, of which 4 lie on dorsal surface and 2 



on or slightly beneath lateral margins of body . . . sexlineatum 



6. With large black or brown marking on dorsal side of head . . 7 



6. Head without conspicuous marking 8 



7. Cephalic marking wreathlike; reddish brown both above and 

 below, except head which is white with a sharply marked dark 

 brown or black wreath on dorsal surface T. signifer 



7. Cephalic marking triangular or shield shaped ; color highly vari- 

 able except head, which is white with shield-shaped or triangular 

 marking of dark brown color on dorsal surface; dorsal surface 

 of body purple, brown with white dorsal longitudinal band, 

 reddish with brown flecks, pale brownish or buff, sometimes 

 with series of narrow transverse white markings . . T. nigrifrons 



