<Tr> <Th> FMA </Th> <Td> 49157 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terms of muscle (edit on Wikidata) </Td> </Tr> <P> The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris . It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil . </P> <P> It is found in vertebrates and some cephalopods . </P>

What type of muscle is in the iris