  We studied the crystal and magnetic structure of the
La$_{1-x}$Ca$_{x}$MnO$_{3}$ compound for $x=0.8$ and $x=0.85$. At T=300 K both
samples are paramagnetic with crystallographic symmetry $Pnma$. At low
temperatures they undergo a monoclinic distortion from orthorhombic $Pnma$-type
structure with $a_p\sqrt{2}\times 2a_p\times a_p\sqrt{2}$ to a monoclinic
structure with ($a_p\sqrt{2}\times 2a_p\times a_p\sqrt{2}$,
$\beta=90+\epsilon\sim 91.4^{\rm o}$) and $P2_1/m$ space group below $T_N$. The
onset of the structural transformation coincides with the development of the
$C$-type long range antiferromagnetic order with propagation vector ${\bf
k}=({1/2},0,{1/2})$. The monoclinic unit cell allowed us to determine the
direction of the Mn magnetic moment with respect to the crystallographic axes:
it is perpendicular to the propagation vector, ${\bf m}\perp {\bf
k}=({1/2},0,{1/2})$. The amplitude of the ordered magnetic moment at $T=1.6$ K
is found to be $2.53(2)$ and $2.47(2)\mu_{B}$ for $x=0.8$ and 0.85,
respectively.
