black snake with red belly and yellow ring around neck
Ring-necked snake Its dorsal coloration is solid olive, brown, bluish-gray to black, broken only by a distinct yellow, red, or yellow-orange neck band.[6][7] A few populations in New Mexico, Utah, and other distinct locations do not have the distinctive neck band.[6] Additionally, individuals may have reduced or partially colored neck bands that are hard to distinguish; coloration may also be more of a cream color rather than bright orange or red.[7] Head coloration tends to be slightly darker than the rest of the body, with tendencies to be blacker than grey or olive.[7] Ventrally, the snakes exhibit a yellow-orange to red coloration broken by crescent-shaped black spots along the margins.[6] Some individuals lack the distinct ventral coloration, but typically retain the black spotting.[7] Rarely, do individuals lack both the ventral and neck band coloration; so the use of those two characteristics is the simplest way to distinguish the species.[6]
Snake The snake's heart is encased in a sac, called the pericardium, located at the bifurcation of the bronchi. The heart is able to move around, however, owing to the lack of a diaphragm. This adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus. The spleen is attached to the gall bladder and pancreas and filters the blood. The thymus is located in fatty tissue above the heart and is responsible for the generation of immune cells in the blood. The cardiovascular system of snakes is also unique for the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart.[55]