400 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
This beautiful Nereid is a tube-dweller. The secretion is fur¬ 
nished by the large glands opening on the dorsal aspect of the 
upper lobes of the feet (Figs. 44, 45^/, PI. 4), and is poured out so 
rapidly and copiously that a new tube is formed in a very few 
minutes when a worm is removed from its tube and placed in a jar 
of clean sea-water. The tube is rather tough and leathery, but 
very flexible and translucent, especially when newly secreted. The 
worms are gregarious, and great tangled ropy bunches of “ eel- 
grass” ( Phyllospadix) are often found, held together by the power- 
fully-adhesive secretion of a colony of N agassizi. The species 
attains sexual maturity at the latitude of San Francisco in February 
and March. I have rarely seen the Heteronereis of this species. 
N agassizi does not attain a large size. The largest I have col¬ 
lected measures 63 mm. in length and 5 mm. in diameter, including 
parapodia and setae. Several small specimens have been brought 
from Puget Sound, and I have collected it at various points along 
the California coast as far south as Santa Barbara. 
16. Nereis cyclurus Harrington. PI. 4, fig. 46. PI. 5, 
figs. 48-52. 
Nereis cyclurus Harrington. Trans. N. Y. acad. sciences, vol. 
16, 1897, p. 214. Pis. 16-18. 
This remarkable species has been ably described by Harrington 
(’97), and its extraordinary commensalistic relations with the Her¬ 
mit crab ( Eupagurus armatus Dana) are discussed. The scanty 
material at command does not enable me to add anything of value. 
One of the striking features of this Nereid is the immense size and 
cup-like form of the peristomium (Figs. 46-48). This is undoubtedly 
for the protection of the prostomium, which when retracted is par¬ 
tially concealed within the concavity of the peristomium. 
17. Nereis procera Elders. PI. 4, fig. 47. PI. 5, figs. 53-59. 
Nereis procera Elders. Die borstenwiirmer, 1868, p. 557. 
PI. 23, fig. 2. 
A very slender Nereid obtained by the Columbia Expedition 
undoubtedly belongs to this species. There are several specimens, 
none of which is complete. The species does not occur in the 
other collections from the Sound. There are no data as to depth 
or locality. 
It is highly probable that this is the species of Nereis mentioned 
by Harrington and Griffin (’97a, p. 156) as dwelling in the tubes of 
a Chaetopterid. The extremely attenuated form of the body and 
