440 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
incurred the writer's deepest obligation. The writer is also indebted 
to Dr. R. Hartmeyer of Berlin, for much important information 
regarding European species, and for specimens of many of the latter 
for comparison, and to Professor A. G. Huntsman of Toronto for in- 
formation concerning the collections he has made in Canadian waters. 
Review of Literature. 
The earliest work known to the writer that requires consideration 
here is that of Lesueur (1823, see list of literature at end of paper). 
He describes and figures several simple ascidians from the Atlantic 
coast of the United States, two of which, Ascidia plicata, sp. no v., 
Ascidia ovalis, sp. nov., were found on a ship's bottom at Philadelphia. 
Though Lesueur's descriptions and figures show external characters 
only, his Ascidia plicata is doubtless the animal described in this 
paper as Tethyum plicatum. The Ascidia ovalis, the writer does not 
venture to identify with any species here described. The types of 
these species do not appear to have been preserved, as a letter of 
inquiry addressed to the Philadelphia Academy of Natural Sciences, 
(where, according to Lesueur, the types were kept), brought out the 
information that nothing was known of the specimens. 
Couthouy (1838) lists the following from Massachusetts: 
Ascidia rustica Linnaeus = Caesira manhattensis } 
Ascidia viicrocosmus Cuvier = Tethyum partitum (probably). 
Ascidia intestinalis Linnaeus = Cionaintestinalisvar.tenella. 
Ascidia pedunculata Lamarck = Pyura ovifera. 
Gould (1841) in his " Report on the Invertebrata of Massachusetts," 
lists : 
Ascidia rustica Linnaeus = Caesira manhattensis. 
DeKay (1843) in the Zoology of New York, part 5, describes: 
Boltenia reniforttiis Macleay = Pyura ovifera 
and records and figures: 
Ascidea manhattensis, sp. nov. = Caesira manhattensis 
both species from New York Harbor, where, however, the former has 
never since been found. DeKay also lists as " extra-limital " forms 
I In listing the species recorded by the several authors, the names adopted in this 
paper are given in the second or right-hand column. 
