No. 464.] STAGES IN LAGENIDE 541 

Cristellaria.— The initial chamber or proloculum of Cristel- 
laria, as in the other genera of the family, is simple and Lagena- 
like (Pl. 1, Fig. 6). The second chamber is added obliquely 
(Pl. ı, Fig. 7), as in some species of Nodosaria, and at this 
stage simply reveals the fact that it will not be a Lagena nor 
any of the straight Nodosarian forms. The third chamber of 
Cristellaria adds a decidedly new character. Instead of con- 
tinuing on as in Nodosaria, it extends back on its inner margin 
so as to come in contact with the proloculum or initial chamber 
initiating the feature of coiling (Pl. 1, Fig. 8). In Cristel'aria 
this coiled character is maintained throughout further growth 
in typical species as in Figs. 9, 18, 19. In further growth the 
shell may take on a flattened form as in Crzstellaria compressa 
d'Orb. or may later take on a loose-coiled, or straight form 
of growth as in the species C. szddalliana Brady (Fig. 21) and 
C. tenuis Bornemann (Fig. 12) which are at present included 
in the genus. The typical Cristellaria is marked by the coiled 
form as the acme of its development (Figs. 18, 19), with a result- 
ing close-coiled form throughout its life history beginning with 
the third nepionic chamber. 
As with Nodosaria, a formula may be made to represent the 
stages in development. In Cristellaria it is the third chamber 
which is the determinative one, and the formula for the close- 
coiled form (Fig. 18) would be, Cristellaria = L+N +C. The 
absence of repetition of any letter in the formula indicates 
progressive development as a coiled form, as no senescence is 
seen in the form or arrangement of the chambers in typical spe- 
cies which are close coiled in the adult. 
Cristellaria as at present recognized contains species showing 
excellent differences in the degree of acceleration of develop- 
ment. In such species as C. articulata Reuss (Fig. 9), the ciose- 
coiled character after being taken on, extends throughout the 
succeeding life history. In others, as C. siddalliana Brady (Fig. 
10), the main part of the shell is close-coiled but towards the end 
of its growth there is an uncoiling seen in the last three cham- 
bers of this specimen. This is brought about by the failure of 
chamber 21 to extend back to the preceding coil and the con- 
tinued shrinking away of the next-formed chambers, 22 and 23. 
