Let
n
≥
3
,
n\geq 3,
and let
Y
Y
be a simply connected, simple algebraic group of type
D
n
+
1
D_{n+1}
over an algebraically closed field
K
.
K.
Also let
X
X
be the subgroup of type
B
n
B_n
of
Y
,
Y,
embedded in the usual way. In this paper, we correct an error in a proof of a theorem of Seitz (Mem. Amer. Math. Soc. 67 (1987), no. 365), resulting in the discovery of a new family of triples
(
X
,
Y
,
V
)
,
(X,Y,V),
where
V
V
denotes a finite-dimensional, irreducible, rational
K
Y
KY
-module, on which
X
X
acts irreducibly. We go on to investigate the impact of the existence of the new examples on the classification of the maximal closed connected subgroups of the classical algebraic groups.