(a) Whenever a species which is not Endangered or Threatened closely resembles an Endangered or Threatened species, such species may be treated as either Endangered or Threatened if the director makes such determination in accordance with section 4(e) of the Act and the criteria of paragraph (b) of this section. After the Director has made such determination in accordance with the notification procedures specified in the Act, such species shall appear in the list in § 17.11 (Wildlife) or § 17.12 (Plants) with the notation "(S/A)" (similarity of appearance) in the "Status" column, following either a letter "E" or a letter "T" to indicate whether the species is being treated as Endangered or Threatened.(b) In determining whether to treat a species as Endangered or Threatened due to similarity of appearance, the Director shall consider the criteria in section 4(e) of the Act, as indicated below: (1) The degree of difficulty enforcement personnel would have in distinguishing the species, at the point in question, from an Endangered or Threatened species (including those cases where the criteria for recognition of a species are based on geographical boundaries);(2) The additional threat posed to the Endangered or Threatened species by the loss of control occasioned because of the similarity of appearance; and(3) The probability that so designating a similar species will substantially facilitate enforcement and further the purposes and policy of the Act.42 FR 32377, June 24, 1977, as amended at 81 FR 51605 , Aug. 4, 2016