Fiddler ray snouts are translucent. The fiddler rays are also distinguished from other guitarfishes in that the anterior nasal flaps of their nostrils are expanded backwards and fused together into a nasal curtain that reaches the mouth. Fiddler rays feed on bottoms shellfish, crabs, and worms, which they crush between their jaws. The eastern fiddler ray is known to scavenge from fish traps. Like other guitarfishes, fiddler rays are ovoviviparous. The egg capsules of the southern fiddler ray are reported to be golden in colour, containing three embryos each. It gives birth to litters of four to six young per breeding cycle.
On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection the connection between natural selection and systems theory. On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection is the title of a joint presentation of two scientific papers to the Linnean Society of London on 1 July 1858: "On The Tendency of Varieties to Depart Indefinitely from the Original Type" by Alfred Russel Wallace and an "Extract from an unpublished Work on Species" from Charles Darwin's "Essay"