251 
upper latus is seen; on the other hånd a subcarina is broad, and 
better developed than in any other of the specimens investigated; in 
this specimen (nr. V of the table) there is a pronounced tendency to- 
wards a development of two distinet rows of small basal latera, the 
plates of the upper row being a little larger. They all have the 
typical finger-like shape as in other specimens. 
I should probably have regarded the species as a Mitella , in 
spite of the finger-like, smaller latera which, indeed, only show 
little difference as compared with Mitella mitella (Lin.). But the 
occurrence of a complementary male makes it necessary to place 
the present species in a genus of its own. The crown of small 
latera strongly contrasts with Calantica, with which genus Proto- 
mitella is otherwise nearly related. 
Genus Mitella. 
The find of Protomitella, and the development of the Mitella 
species described below not only throw new light on the affinity 
and phylogeny of the genus Mitella itself, but also provides us with 
a base from which we may judge of the phylogenetic affinity of 
the species within the genus. 
The most primitive group among recent species is the sertus- 
group, characterised by a low development of the latera; only the 
rostrum has attained a higher development as in the preceding 
genus; the latera do not mueh surpass the peduncle scales in size, 
and none of them predominates the others. — The next stage is 
found in Mitella mitella where an upper latus is well developed, 
and mueh larger than the other latera, being only a littlle smaller 
than the rostrum. In the pollicipes- group on the other hånd, as 
here illustrated by Mitella polymerus, also other latera emancipate 
themselves from the lower row, and in this way the skeleton of 
the capitulum becomes more complicated. We are able to charact- 
erize an upper latus, a carinal, an inframedian, a median, and a 
rostral latus; but it is not probable, that these plates really are 
homologous with the plates of Scalpellum, referred to by the same 
names. Quite on the contrary, the development seems to indicate 
that here we face a convergency, which cannot be taken as proof 
of a phylogenetic relation. 
