4 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



Among the features common to the Gastropoda of both the upper 

 Cretaceous and Eocene, one is quite conspicuous. It is the fre- 

 quency with which forms of diverse lineage develop a tendency to 

 produce a coat of enamel over the whole surface of the shell, often 

 very profusely, in species belonging to groups which in the recent 

 fauna have not the habit. As examples, reference may be made to 

 such forms as Volutomorplia, Liopeplum, Liomelon, Athleta, and 

 Psilocochlis, while numerous others will occur to the reader. 



We may now proceed to examine the Volutoid population of dif- 

 ferent upper Cretaceous districts, where the invertebrate fauna has 

 been well worked out or is sufficiently known. 



The chief districts are situated in India ; in the Gosau district of 

 the eastern Alps, and the Aachener chalk of northern Germany ; the 

 Greensand marls of New Jersey, the Ripley group of the Gulf 

 States, the Pugn ell us sandstone at the top of the Benton group in 

 Colorado, and the Chico group of California. These range from the 

 middle (Turonian) to the uppermost Cretaceous. 



Dr. Stanton, while disclaiming the practicability of exact correla- 

 tion between the subdivisions of the Cretaceous in the United States 

 and those of foreign countries, is disposed to regard the Colorado, 

 Trichinopoly, Chico, and Gosau horizons as in part representing the 

 Turonian, while Ripley and Aachen correspond to some portion of 

 the Senonian. 



In India the fauna of the series known as the Trichinopoly group 

 has been discussed by Sowerby, Forbes, and Stoliczka. The latter 

 author had an unfortunate tendency toward uniting under one spe- 

 cific name very different things, if only they possessed a superficial 

 resemblance — a course more fatal to scientific accuracy than going 

 to the opposite extreme. However, he worked with great industry 

 and erudition and gave good figures of the fossils, so that paleontol- 

 ogists are under serious obligations to him for his work in India. 

 His early review of the Gosau fauna was hasty and insufficient ; it is 

 replete with erroneous conclusions. Zekeli, whom he criticized 

 severely, is — if any confidence is to be placed in the illustrations of 

 his monograph — a far more discriminating author than his critic.' 

 Naturally, in the discussion of these exotic faunas one must assume 

 that the illustrations of a reputable author are at least approximately 

 accurate in depicting the species figured. 



The Volutidse of the Trichinopoly group, with one or two excep- 

 tions, have a somewhat similar sculpture while varying widely in 

 form. The slender, widely separated spiral ridges are more pro- 

 nounced than the axial sculpture, in proportion to their size the 



