A New Triassic Ammonite from Yanaizu, North of Inai near Ishinomaki, Miyagi Prefecture

Several months ago,. Mr. F. Ueda, teacher of the Toyoma High School, Miyagi Prefecture, showed the writer a peculiar ammonite from a Triassic sandy argyllite exposed at Yanaizu, 12 km south of Toyoma and 20 km north of Inai near Isinomaki. This ammonite attracted the writer's attention on account of the unusual growthform of its last whorl, which is first produced linearly and then incurved again as in the Jurassic Macroscaphites and the Cretaceous Scaphites, while it resembles, in its coiled part, Danubites japonicus Shimizu 1> from the Anisic Hollandites beds of Inai. The annexed figure shows this specimen in natural size. All specimens of the Anisic ammonites from the Hollandites beds of Inai are moulds, the shell-substance being never preserved. The moulds are always one-sided ; that is to say, there is no specimen ever seen by the writer, with both surfaces preserved. Moreover, the majority of the specimens are obliterated in a definite manner, lengthened in one direction and correspondingly shortened in the other, due to lateral presure. The present specimen from Yanaizu is in the same mode of preservation. The Yanaizu specimen consists of a coiled part and an uncoiled, key-shaped part; the dimensions of the coiled part are :