  We describe a Hopf ring structure on the direct sum of the cohomology groups
$\bigoplus_{n \geq 0} H^* \left( W_{B_n}; \mathbb{F}_2 \right)$ of the Coxeter
groups of type $B_n$, and an almost-Hopf ring structure on the direct sum of
the cohomology groups $\bigoplus_{n \geq 0} H^* \left( W_{D_n}; \mathbb{F}_2
\right)$ of the Coxeter groups of type $D_n$, with coefficient in the field
with two elements $\mathbb{F}_2$. We give presentations with generators and
relations, determine additive bases and compute the Steenrod algebra action.
The generators are described both in terms of a geometric construction by De
Concini and Salvetti and in terms of their restriction to elementary abelian
2-subgroups.
