456 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
extensive lists given by Hartmeyer (1903). Many important refer- 
ences that are of too recent date to appear in the above work of Hart- 
meyer have, however, been inserted. 
Owing to the difficulty frequently encountered in identifying asci- 
dians, even with lengthy descriptions and good figures, the value of 
analytical keys and synopses of characters for the purpose is doubtful. 
If those here offered occasionally give a hint that is of assistance, it 
will be all that is expected. 
Ahhrevialions used in Illustrations. 
at — atrial aperture. tndv — rriedian dorsal vessel. 
br — branchial aperture. od — oviduct. 
dl — dorsal lamina. oc — esophagus. 
en — endostyle. ov — ovary. 
fd — fold . r — rectum. 
g — gonad. rep — • reproductive glands. 
gc — gastric caecum. s — stomach. 
i — intestine. sd — sperm duct. 
ilv — internal longitudinal vessel. sg — stigmata. 
k — kidney. t — testis. 
I — Hver. tv — transverse vessel. 
The illustrations are from drawings and photographs by the author. 
The photographs are from alcoholic specimens. The text-figures 
show the outline of the body after removal from the test (except 
text-fig. 12). 
Family CAESIRIDAE Hartmeyer, 1908. 
[= MOLGULIDAE auct. plur.]. 
Branchial aperture usually with six lobes; atrial aperture usually 
with four lobes. Body frequently not permanently attached, the 
animal living buried in the sand or mud of the sea bottom. 
Tentacles almost always branched (simple in one New England 
species). 
Branchial sac with internal longitudinal vessels and generally with 
longitudinal folds and inwardly projecting conical elevations or 
infundibula, whose walls are pierced with curved, spirally arranged 
stigmata, straight stigmata being the exception in this family. Intes- 
tine always on left side of body. Reproductive organs sometimes 
on one, but more frequently on both sides of body. 
An excretory organ or kidney consisting of a large completely 
