590 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
which spreads out over the shell to which it is attached. Apertures 
moderately prominent; surface of test nearly smooth. 
Gulf of Saint Lawrence, locality illegible. Collected by J. F. Whit- 
eaves. Two specimens having the dorsal surface finely wrinkled ; the 
largest 14 mm. long by 10 mm. wide, exclusive of the border of test 
substance which spreads out over the surface to which the body is 
attached. 
Eastport, Me., six specimens of oval outline when seen from above 
and of a low, more or less flattened dome-like form. Apertures not 
prominent or only slightly so; surface of test wrinkled. None exceeds 
the above dimensions. 
These specimens, collected during the summer, contained tailed 
larvae in the peribranchial cavity. 
Family RHODOSOMATIDAE Hartmeyer, 1908. 
Tentacles simple. 
Branchial sac without folds but with internal longitudinal vessels 
(sometimes incomplete or rudimentary) which bear no papillae. 
Dorsal lamina broken up into a series of languets. 
Intestine variable in position, more commonly on the right side. 
Middle part of intestine passes below the stomach instead of above 
as in most ascidians. 
Subfamily Chelyosomatinae Hartmeyer, 1908. 
Stigmata curved, sometimes spiral in arrangemment. 
Key to Genera. 
Upper surface of body protected by regularly arranged horny plates. 
Chelyosotna. 
Body unprotected, often stalked, test thin and transparent. Stigmata in 
spirals; well developed internal longitudinal vessels present Corella. 
Genus Chelyosoma Broderip and Sowerby, 1830. 
Body flattened and protected above with regularly arranged horny 
plates connected by short muscles. Both orifices six-lobed. 
This peculiar genus can be at once recognized by the above char- 
acters. The species found in the New England region was described 
by Stimpson (1852) as distinct from that of Europe, but as Hartmeyer 
(1903) has pointed out, no reasons for considering them distinct seem 
to exist. 
