666 [Vol. 18,

131. A Note on the Japanese Ammonites Belonging to the Caudryceratidae*. By Taturo MATUMOTO. (Comm. by T. KATO,M.I.A., Dec. 12, 1942.) The Japanese fossils of the Gaudryceratidae, one of the important families of Cretaceous Ammonoidea, have been studied by H. Yabe and other Japanese paleontologists. I also had the opportunity of studying the material in connection with the biostratigraphic investi- gation on the Cretaceous deposits of Hokkaido and Karahuto. The following is a short note on the result of my study.' The numerous Japanese specimens so far examined are classified as follows. Family Gaydryceratidae. Genus Parajaubertella; Matumoto nov. P. kawakitana Matumoto nov. (genotype) Genus Anagaudryceras, Shimizu emend. A, sacya (Fortes) em. (genotype) A. sacya var. plicatocostata Matumoto MS. A. limatum (Yabe) A. yokoyamai (Yabe) A, ryugasense Matumoto MS. A. madraspatanum (Blanford) Genus Gaudryceras, Grossouvre em. G. denseplicatum (Jimbo) G. denseplicatum var. intermedia (Yabe) em. G. denseplicatum var. kawadai Matumoto MS. G. tenuiliratum Yabe em. G. tenuiliratum var. frequence Matumoto MS. G. tenuiliratum var. substriata Matumoto MS. G. tenuiliratum var. ornata Yabe G. striatum (limbo) (=? G, sachalinensis (Schmidt)) G. striatum var. paucistriata Matumoto MS. G. striatum var. picta Yabe G. striatum var. lata Matumoto MS. G. crassicostatum (Jimbo) G. subcostatum Matumoto MS. Genus Zelandites, Marshall em. Matumoto Z. odiensis (Kossmat) Z, odiensis var. lateumbilicata Matumoto MS. Z. mihoensis Matumoto Z. mihoensis var. capricornus Matumoto MS. Z. kawadai (limbo) em. Z. varuna (Forties) var. japonica Matumoto Z. sp. (n, sp. ?) A close investigation of the ontogenetic development enables us to elucidate the proper systematic position of species and genera. Not- * The three papers presented at this meeting are brief reports on my researches on Cretaceous ammonites. I wish here to express my thanks to the Imperial Academy for their grant in aid of this research. I am also indebted to Prof. T. Kato, Prof. Emeritus H. Yabe, Prof. E. Konno, and Prof. T. Kobayashi for their constant encoura- gement during the course of these studies. 1) A monograph on the Cretaceous Ammonites of Japan will be published in the Memoirs of the Kyusyu Imperial University.

} No. 1U.] A Note on the Japanese Ammonitesbelonging to the Gaudryceratidae. 667 withstanding the considerable diversities and variabilities of characters in their later stages, all the forms listed above are of the same type in their nepionic stage, and bear typical lytoceratoid characters (Cf. Fig. 1). A careful examination of many examples convinces me that the suture-line-formula" is invariably I. U, = S. U.. L, E, the lobes E. L

Fig. 1. Gaudryceras tenuiliratum Yabe.

a. Whorl sections of young shell (diam.= 13.2mm). b. Lateral and apertural view of the primitive stage. C. Protoconch and a whorl section of the first volution. d. Development of suture-line (d,=second suture-line, d6=suture- line at the early substage of the third volution). e. Suture-line of the seventh volution (when diam.=38 mm). and U2 and the intervening saddles characteristically bifid ; the internal lobe I is extraordinarily developed showing the so-called septal-lobe2'. Parajaubertella, a new genus which is based on a Japanese species (P. kawakitana Matumoto, sp. nov.)" is very interesting, because it

1) I doubt very much whether Schindewolf's observation on the suture-line of Gaudryce'ras is correct. (Abh. d. preuss. geol. Landesanst., N. F. 115, 1929). 2) The "septal lobe" is found also in the Tetragonitidae, being probably a characteristic feature of the lytoceratids. 3) Following is an abstract from my- full description (MS.) of the species Para- ja ubertella kawakitana Matumoto : Shell subangustumbilicate, oligogyral ; whorls of immature stage depressed, semilunate in cross-section with an arched venter and a deep umbilical wall, increase in the size, particularly the height, of the whorls very rapid, resulting in a mature shell which has a slightly compressed and rounded whorl, and which is subgradumbilicate. Shell frequently constricted in later substage of the primitive stage, laevigate and with frequent, very narrow, and faint furrows in the earlier ages, tending to have weak radial furrows and the intervening radial bands in more or less late substage of immaturity, till it acquires more distinct furrows and broadly round-topped ribs in full grown age. Suture-line gaudryceratoid with a formula 1, U1=S, U2, L, E, and with a peculiarity of lobes and saddles at the umbilical, shoulder. 'f 668 . MATUMOTO. [Vol. I8,

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o w~ No. 10.] A Note on the Japanese Ammonitesbelonging to the Gaudryceratidae. 669

resembles Gabbioceras or Jaubertella'' of the family Tetragonitidae es- pecially in the shell-form of the middle-stage, although other characters as well as its ontogenetic development are rather gaudryceratoid, the genus being allied in certain respects to Eogaudryceras and Anagau, dryceras (Cf. Fig. 2). Genus Anagaudryceras is characterized by the fine striation of its shell throughout its life and broad or narrow oostae in the adult stage, the ornamentaations showing less fiexuosity. while genus Gaudruearn..q

1 "._____J

Fig. 3.

(s.s.) is characterized by moderately flexiradiate and diverging striae and subcostae, broad or narrow costae being also found in adult form. The two genera differ very little in shell-form as well as in suture-line, Genus Zelandites, as was illustrated in detail in my former paper, is a specialized form which is charaterized by a comparatively small size, much compressed shell-form, narrow umbilicus in the later stage, weak ornamentation, and a peculiar feature in its suture-line. The remains of the Gaudryceratidae are quite abundant in the

1) The two genera are possibly synonymous, Jaubertella being apparently based on an immature shell. 2) Matumoto, T.: Zelandites, a genus of Cretaceous Ammonites (Japan. Jour. Geol. & Geogr., vol. 15, 1938). 670 T. MATUMOTO. [Vol. 18,

Japanese Cretaceous. From my careful biostratigraphic investigations'' the geological range of the species in the Cretaceous province of Hok- kaido and Karahuto is summarized in Fig. 3. And the stratigraphic occurrence of the fossils in other areas of Japan so far known seems to be in harmony with this result. As is clearly illustrated in the chart, the geological range of the species and genexa of the Gaudryc~ratidae is generally quite long . Nevertheless, owing to abundant occurrence, the fossils are useful for correlation and classification of strata, especially when the co-existent relation of more than one species is considered. From these Japanese materials as well as the hitherto known foreign ones, we can state that a diverging differentiation of the lytoceratids occurred in the late epoch of Paleocretaceous Period, giving rise to various genera of the Gaudiyceratidae and the Tetragonitidae. Of these genera, some became extinct in the epoch, but others persisted and flourished till the end of the Neocreta ceous Period, giving rise to various species and varieties. And many representatives of the family were distributed in the Japanese province although a peculiar form like Vertebrites2' has not yet been detected. Noteworthy is the fact that the morphogenesis presented by the Japanese species of Gaudryceras is subparallel to that of Anagaudry- ceras. Between the species of Gaudryceras, a morphologically serial change is found, while a morphologically hyatal relation seems to be in general in Anagaudryceras. The genus Zelandites is not- represented by a single orthogenetic series of species, but comprises a number of parallel and special offshoots of the family,

1) Matumoto, T.: Fundamentals in the Cretaceous Stratigraphy of Japan (Mem . Fac. Sci., Kyiasyt Imp. Univ., ser. D, vol. 1 & vol. 2, 1942). 2) Gaudryceras crasrieostatum (Jirnbo) and G. tenuiliratum var. 6rnata Yabe are not referable to Vertebrites, because they do not possess the peculiarity of internal suture line like Vertebrites, although in shell-form and in ornamentation there is some resemblance.