392 THE AMERICAN NATURALIST, [VoOL. XXXV. 
Gonosome : Gonangia differ in the two sexes. Male elongate, slender, 
tapering toward base and expanding toward orifice, which bears four stout 
spines. Female gonangium oval, deeply cleft above into four leaf-like seg- 
ments, larger than male. 
2, D. rosacea Linn. 
Trophosome: Stems slender and delicate, branches alternate and with 
internodes constricted at the base. Hydrothece long, tubular, with upper 
portion free and divergent toward 
the aperture, which is oblique and 
entire. 
Gonosome : Gonangia slightly 
different in the sexes; female pear- 
shaped, elongate, borne on short 
pedicels and marked with eight lon- 
gitudinal ridges, each terminating 
above in a spinous process. Male 
somewhat curved toward base, with 
similar longitudinal ridges terminat- 
ing in spinous teeth about the slender 
tubular orifice. 
Thuiaria Flem. 
A single species of this genus 
comes within the present synopsis. 
Thuiaria thuja Flem. 
Trophosome : Stem and branches 
rather rigid, somewhat zigzag in 
shape, and annulated near the base. 
Perisarc black or very dark in color. 
Hydrothece smooth, ovate at base 
and tapering toward the distal end. 
Gonosome: Gonangia smooth, 
pyriform, and with circular slightly 
Fic. 28. — Hydrallmania falcata Linn, c 
(After Hincks.) emarginate aperture. 
Hydrallmania Hincks. 
Hydrallmania falcata Linn. (Fics. 28, 29). 
(Sertularia falcata.) 
Trophosome: Stems flexuous, slender, sometimes spirally inclined. 
Branches alternate, regularly pinnate and plume-like, arising just above 
