The knowledge that certain animals produce faeces of characteristic form is not of recent date, and the fact has been commented on for many years. The occurrence of small ovoid masses, sometimes glauconized or pyritized, in recent as well as fossil marine deposits, has also been recorded, but it is only recently that the identity of some of these bodies with animal faeces has been recognized with certainty. As early as 1678 Martin Lister (9), speaking of mollusca, said in his Historia Animalium TractatusPraeterea, ex excrementarum differentia, certum est intestinorum figuram aliam atque aliam esse in diversis speciebus.
and again, referring to Viviparus,
Illud singulare, ei esse excrementa figurata, exigua ad modum et figuram hyperici seminis, etiamsi sit bestiola aeque magna ac quaevis chochlea terrestris. Plurima excrementa simul ejecit, velut oves aut cuniculi.
Since that date various authors have figured or described the faeces of particular species, for example, Pecten sp. (8), Mytilus edulis (2, 20), Littorina sp. (20), Tegula funebrale (7), and in particular the faeces of a number of species of molluscs and Crustacea have been figured by Moore (11, 12, 13, 14, 15, 16).
The forms of these faeces vary extremely: in many marine animals the faeces are of indeterminate shape, or of such loose consistency that they can not survive free for any length of time. Of such are the faeces of most fishes and many Crustacea. In general, carnivorous animals tend to produce faeces of loose consistency, vegetable eaters firmer ones, and deposit eaters the most resistant of all.
