APROPOS of Dr. Eastman's letter on the 'stomach stones' of the plesiosaurs, published in SCIENCE, No. 510, p. 465, permit me to state that there is not a shadow of doubt that the plesiosaurs, both Cretaceous and Jurassic, had the habit of swallowing such stones. At least. thirty instances are now known of the occurrence of the very peculiarly worn pebbles between the ribs or with the remains of plesiosaurs in both Europe and America. The fact was first published by Professor Seeley, of England, in 1877, and Seeley it was who first suggested their use in digestion and the possession of a 'gizzard' by these animals. This absolves Mr. Brown. Crocodiles are frequently reported to have like habits, and Buckland says that the Arabs determine the age of these animals by the number of the stones found in the stomach, one being swallowed each year! Similar pebbles have also been found with the remains of extinct crocodiles, and St. Hilaire gives a minute account of such instances. I need not say also that there are various accounts in the literature of like habits possessed by some of the seals and sea-lions. I doubt not that the habit was an intentional one with the plesiosaurs, nor do I think that Dr. Eastman would doubt either, had he ever collected the remains of these animals in the field. That the p1esiosaurs had a gizzard-like stomach I do not believe, but I see nothing startling in the suggestion - with due apologies to Dr. Eastman. His argument, that, if the plesiosaurs were of lithophagous proclivities, other reptiles should be expected to gorge themselves on a like mineralogical diet is hardly pertinent. The prairie chicken has the regulation gallinaceous gizzard, and, therefore, the sage hen should have one. But it has not. Ab uno disce omnes is not always safe. And, it must be remembered, all reptiles have stomachs with thick muscular walls.

S. W. WILLISTON.