170 
P, resembles P,, but is only 8 mm, long and proportionately less 
stout; the following pinnules are small and weak. 
When I established the genera Dichrometra and Stephanometra 
I was in considerable doubt in regard to the systematic position 
of this species. In the original description Carpenter mentions the 
lateral processes on the rays, but fails' to state whether the large 
lower pinnules are spine-like in character or flexible; his figure, 
however, appears to represent a species of Dichrometra. The pre- 
sent specimen shows that marginata is a typical Stephanometra, 
nearly related to 5. monacantha. 
Stephanometra tenuipinna (Hartlaub). 
Antedon tenuipinna 1890. Hartlaub, Nachr. Ges. Gåttingen, Mai, 1890, 
BR Se Syre 1909. A.H. Clark, Proc. Biol. Soc. Washing- 
ton, Vol. 22, p 
SEE June 17, 1904. One specimen with twenty- 
four arms 70 mm. long; one ray bears eight arms, two two, one 
seven, and one five, in the latter one of them springing direct 
from a IBr axillary. 
This specimen agrees very well with Hartlaub's description, 
except that P, is nearly as long as P,, and P, is as he deseribes 
P,. The rays have slight marginal projections. 
In my original diagnosis of the genus Stephanometra I men- 
tioned the development of lateral processes on the outer sides of 
the rays as a generic character, but in a footnote I stated that 
these were absent from S. tenuipinna, possibly because of the im- 
maturity of the type (and only known) specimen. It was with 
considerable satisfaction, therefore, that in this second specimen I 
found them to be developed as in the other species of the genus, 
though not quite so large as usual. 
Genus Mariametra A. H. Clark. 
Mariametra 1909. A. H. Clark, Proc. Biol. Soc. Washington, Vol. 22, 
p. 144. 
