The Annulation of the external surface is due to numerous thickened areas of the ectocyst which take the form of slender rings surrounding the zooecium; they are most conspicuous on its distal half.
"Freshwater Sponges, Hydroids & Polyzoa"
Nelson Annandale
This monkey is one over which many naturalists have argued; it is synonymous with Macacus speciosus, M. maurus, M. melanotus, and was thought to be with M. brunneus till Dr. Anderson placed the latter in a separate species on account of the non-Annulation of its hair.
"Natural History of the Mammalia of India and Ceylon"
Robert A. Sterndale
The two former of these, therefore, conform to the type of S. pygerythrus, but the fur of the upper parts is greyer and not so richly coloured as in it, but the Annulation of the fur has the same character in both.
"Natural History of the Mammalia of India and Ceylon"
Robert A. Sterndale