32 EDWARD T. BROWNE. 
Famity MITROCOMIDE (Haeckel, 1879), Torrey, 1909. 
Character of the Family.—Leptomeduse with open sensory pits on the velum, 
containing otocysts. 
In the summer of 1908, I began a revision of the Leptomeduse with open 
sensory pits, but circumstances arose which compelled me to lay aside the work before 
the critical examination of the species was finished, and even now it must be deferred 
for another communication. Prof. Maas, in 1893, practically laid the foundation of 
the family, which he called the Lafoeide; but I agree with Mr. Torrey (1909) that 
Mitrocomide is a better name to use, and it was that which I was going to adopt. 
The hydroid genus Lafoea has no connection with the Meduse belonging to the 
Mitrocomide. Messrs. Maas and Torrey include the genus Halopsis in the family 
with open sensory pits, but in the descriptions given by Prof. Agassiz (1865) and 
Mr. Fewkes (1888) of Halopsis ocellata, which is the type species of the genus, no 
mention is made of the sense organs being open pits. Before Halopsis can be included 
among the Mitrocomide the structure of the sense organs must be re-investigated. 
The family consists of the following genera :— Cosmetirella, Cosmetira, Tiaropsis, 
Mitrocomella and Mitrocoma. I give the characters of the genera and just mention 
the species, but some of the latter have not been critically examined. 
COSMETIRELLA. 
Generic Character.—Mitrocomide with four radial canals; with eight sensory 
pits; without marginal cirri; and without ocelli adjacent to the sense organs. 
This new genus is established to receive a new Antarctic species, described on 
p. 34, under the name of Cosmetirella simplex. This genus corresponds to Phialella 
among the Eucopide. The only real difference between Cosmetirella and Phialella 
is that the former has open sensory pits, and the latter closed sensory vesicles. 
CosmeEtIRA (Forbes, 1848), Hartlaub, 1909. 
Generic Character.—Mitrocomide with four radial canals; with eight sensory 
pits ; with marginal cirri. 
The type species of the genus is Cosmetira pilosella (Forbes). It was originally 
described by Forbes under the name of Thaumantias pilosella, and he proposed 
Cosmetira as a sub-generic name. He never mentioned the existence of sense organs, 
which I found some years ago, when (1896) I temporarily placed the species in the 
genus Euchilota, which has closed sensory vesicles and belongs to the Eucopide. 
Subsequently I noticed that the sense organs were open pits, and realised that the 
species would have to be removed to another genus, for which I selected Forhes’ 
name of Cosmetira. 
