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the surface like small spines, somewhat recalling the appearance 
of the se/fws-group. 
Nevertheless it is not possible to maintain the individual groups, 
here referred to, as representatives of a separate species besides 
Figs. 18 and 19. Mitella polymerus f. echinata from San Pedro, Calif. 
Fig. 18. a mandible, b maxilla, c scale from the middle part of the peduncle. [X 33]. 
Fig 19. a. small specimen with only the three upper, principal latera developed, 
h. somewhat older specimen where the peduncle scales are 
about to appear. [x 44]. 
Mitella polymerus . The features of the animal, its mouth feet 
(Fig. 18), cirri, and appendages entirely agree with the forma typica. 
Owing to the external differences they must nevertheless be re- 
garded as a special variant group, which I have given the name 
of forma echinata, owing to its spring appearance. Later investig- 
ators shall have to find out the special conditions, under which 
this form develops. Some few specimens from Bird Rock near 
La Jolla give evidence that both forms occur near the biological 
station. 
To the peduncle of the greater specimen from San Pedro some 
small specimens were attached; the youngest two are depicted in 
fig. 19. Although they do not exhibit principal differences from the 
Vidensk. Medd. fra Dansk naturh. Foren. Bd. 73. 17 
i 
