No. 464.) STAGES IN LAGENIDA. 539 
DEVELOPMENT OF TYPICAL SPECIES OF VARIOUS GENERA. 
Lagena.— This genus represents the simplest condition seen 
in the family under discussion. In its geological history it can 
be traced from the Silurian to the present time. It is mono- 
thalamous or single-cham- 
bered (Fig. 3) . Ihe 
species very commonly 
develops a neck at the 
anterior end (Figs. 4, 5). 
The variation in forms 
of ornamentation is very 
remarkable and includes 
costae, reticulate patterns, 
knobs, and bosses or 
broadly expanded wings 
of shelly material, but the 
underlying character of 
the chamber is always 
that of a simple flask-like | 
form or a modification of 
it. This simple chamber 
1 5 represents the completed 
eye development of this ge- 
group. Fig. 3, Lagena globulosa Montagu, asmooth nus, which is the only 
type; Fig. 4, Z. salcata W.& J., var. interrupta £ 
Williamson, a costate type; Fig. 5, Z. fi one of the family that 
pee Atc Mas the single-chambered 
character. As it is the 
simplest form in the family and as all the other genera of the 
family start off with a simple chamber which is comparable to 
it, Lagena may be taken as the radical from which other genera 
of the family may be derived. 
Nodosaria.— This genus in its typical form consists of a linear 
series of Lagena-like chambers, the posterior wall of each newly 
added chamber overlapping the anterior wall of the preceding 
one. The initial chamber or proloculum is comparable in char- 
acter to the adult Lagena but the addition of the second cham- 
ber in Nodosaria shows that it is developing beyond the single- 

or Mosa 
