My dear Darwin

The two toed sloth and the black crested the toed Sloth Brady torquatus are Both Sexes alike   But the females Ai (Arctopithecus Gray) are covered with uniform fur varing in length and colour in the different Species   The Male have a path of short shining very soft hair between shoulders¹   In three out of the four species in the B.M this patch is large and of a bright orange yellow color with a central black streak and black spots on the edge²   In the other (A flaccidus) the patch is small and pure white with a short black central streak³

The female of A. griseus⁴ has a small pure white tuft of very soft hair like a powder puff on each side of the back over the loins almos hid from view by the longer hairs of the fur   I have not found these tuft in the females of the other species   Buffon who knew the male of one species called the Ai a dos brulee which Lesson has named Acheus ustus.⁵ Teminck thought the spot was produced by the long hair being worn off⁶

Wagler in 1813 suggested they were the males and lately I have been able to verify the fact⁷

With kindest regards | Ever yours sincerely | J E Gray

I did not learn to write with my left hand until I was more than 70 so excuse its badness⁸