In the 17th and early 18th centuries, however, the term "shagreen" (or "chagrin") began to be applied to a leather made from sharkskin having a curious grain surface of lonzenge-shaped, raised and spiny scales of minute size, the character of which is difficult to perceive without optical assistance. The term was also applied to the skin of a rayfish (probably Hypolophus sephen), which is covered with round, closely set, calcified papillae resembling small pearls. In its natural form it has been used for many years in both the East and the West for a variety of purposes, including bookbinding; however, in the early years of the 18th century it became the practice to grind the surface flat and smooth, leaving only the pattern of small contiguous circles. The leather was dyed from the flesh side so that the dye did not reach the small circles of calcified substance but only colored the epidermis where it could be seen between the circles. This is the leather which for a century has been called "shagreen"; how confusion arose with sharkskin, which is completely different both in character and in appearance, is not clear. (97 , 261 , 351 )