Pectines are comb-like structures, widely found in the biological world. They occur, for example, on the underside of scorpions, where they are used as sense organs. In ducks they are placed on the sides of the bill and serve both as food-strainer and as a comb for preening. The avian eye also contains a structure called a pecten oculi, which is a comb-like projection of the retina. It is thought to enhance nutrition for the cells of the retina. Whales have a similar comb-like structure called baleen. "Pectinate" means supplied with a comb-like structure and is reflected in numerous specific names as "pectinata", "pectinatus" or "pectinatum" or epiteths like Murex pecten.