444 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
and criticised by Verrill (1870b) and the identity of some of the forms 
appearing there as distinct species was pointed out. 
Dall (1870), in his "Revision of the Classification of the Mollusca 
of Massachusetts," took his hst of Ascidians from Binney's work. 
In 1871 the important series of papers by Verrill entitled " Descrip- 
tions of some imperfectly known and new Ascidians from New Eng- 
land," appeared in the American Journal of Science. The simple 
ascidians described in them are as follows : 
Molgula manhattensis (DeKay) = Caesira manhattensis. 
" pannosa, sp. no v. = " pannosa. 
" retortiformis, sp. nov. = " retortiformis. 
" littoralis, sp. nov. = " citrina. 
" papulosa, sp. nov. = " papillosa. 
" pilularis, sp. nov. = Bostrichohranchus pilularis. 
Cynthia stellifera, sp. nov. = Tethyum partitum. 
" monoceros (MoUer) = " rusticum. 
" carnea (Agassiz). = " coriaceum -\- Dendrodoa carnea. 
" echinata (Linnaeus) = Pyura echinata. 
" pyriformis (Rathke) = " aurantium. 
" pulchella, sp. nov. = Dendrodoa aggregata var. pulchella. 
Ascidia complanata Fabricius = Phallusia prunum. 
Ciona tenella (Stimpson). = Ciona intestinalis var. tenella. 
Figures of most of these species are given. These figures and descrip- 
tions (as was also the case with those of the other authors so far re- 
viewed) deal almost exclusively with external characters, though 
unlike those of the earlier authors, they are very detailed, and leave 
little to be desired in so far as information regarding the external 
appearance is concerned. 
In the latter part of the same year, Verrill (1871b) published another 
paper recording many facts about the above species, and in the follow- 
ing year (1872b, p. 209-214), one giving a list of ascidians from the New 
England region not included in Binney's work, and recording the 
changes in the nomenclature of various species which his studies of 
this group had shown to be necessary. That same year (1872b, 
p. 281-290) two more simple ascidians were described by him : 
Glandula arenicola, sp. nov. = Tethyum molle. 
Molgula pellucida, sp. nov. = Bostrichohranchus pilularis (var.?). 
In other papers (1873-'74, 1874a) on the explorations and dredging 
operations on the New England coast, many additional facts about 
