HYDE: CAMAROPHORELLA. 61 
like form, as Dicainara is the only other genus of the subfamily known 
to have a brachial platform. It should be noted that in the youngest 
specimens of Camarophorella observed, the dental lamellae are always 
united and continued to the surface of the valve as a median septum 
much as in the adult, so that there is no known true Meristiform stage. 
^Miether or not Camarophorella has been evolved along some such 
line as that just indicated, if the type of jugum is considered as proof 
of a genetic relationship to Merista, IVIeristella, and Dicamara, it 
must be considered a more highly specialized form in which there has 
existed between the position of the jugum, the musculature, and the 
platforms a much more delicate adjustment than was possible in the 
earlier t>^es. In them the lateral branches of the primary lamellae 
were much longer and were set on the lamellae at fully half their length 
from the crura, the lateral branches were as long as the stem, and the 
lamellae of the jugum did not enter the space between the primary 
and secondary lamellae of the spiralia. The jugum lay wholly in the 
open space within the bases of the cones, and its construction is best 
described as straggly. Compare with this the compact jugum of 
Camarophorella, its short, stubby, lateral branches placed closer to the 
crura on the primary lamellae, its long "stem" (using this unsuitable 
but convenient term) extending obliquely to the ribbons on the oppo- 
site side of the cone, the lamellae of the jugum passing at once to the 
space between the primary and secondary lamellae of the spiralia where 
they continue practically to their point of reunion with the stem; the 
whole presenting a compact structure, suggesting that it is much more 
an intimate part of the brachidium than is the corresponding structure 
in the earlier forms. 
Figure 14 (pi. 7), is a semidiagrammatic attempt to show the arrange- 
ment of the platforms and muscles in relation to the jugum. The 
outline of the shell, the s])ondylium in the pedicle valve and its adductor 
muscle scar, the hinge plate, and crus are correctly drawn from a single 
specimen. To these have been added the brachial platform and 
median septum, the jugum, and the spiral arm. Although the attach- 
ment of the adductor to the brachial platform is represented as ex- 
tending the length of the median septum, it must be remembered that 
the dorsal convergence of the primary lamellae which hang very close 
to the platform, and the angle which the accessory lamellae of the 
jugum make with each other (between 60° and 75°), force the greater 
portion of the area of attachment of the adductors into the posterior 
