Triticitesの殼壁について

On the Wall of Triticites

佐田 公好

廣島大學地學研究報告

Geological report of the Hiroshima University

Through the courtesy of Professor Ryuzo TORIYAMA, I had an opportunity of studying the spirothecal structure of some typical species of Triticites, T. secalicus (SAY) and T. ventricosus (MEEK and HAYDEN), all from U.S.A. I also had a good chance to examine the original specimens of Triticites described by such authors as TORIYAMA (1958), KANMERA (1955), IGO (1957) and KANUMA (1958) from Honshu and Kyushu of Japan.
In Triticites secalicus (SAY) (PL. 22, FIGS. 2-4) and T. ventricosus (MEEK and HAYDEN) (PL. 22, FIGS. 5-6), the former was obtained from the Baral Kereford Limestone and the Upper Hen-mander Shale of Nebraska and the latter from the Hughos Creek Shale of Blue Mountain, Manhattan, Kansas, the spirotheca is composed of a tectum and the upper and lower tectoria in the first three to four volutions, in the succeeding one volution it is four layered wall consisting of a tectum, a diaphanotheca, and the upper and lower tectoria, but beyond the fifth to the sixth volution the spirotheca is composed of a tectum and a keriotheca with alveoli.
When KANMERA (1955) described Triticites matsumotoi (p. 184, pl. 11, figs. 6-25) from the Yayamadake Limestone, he stated that in mature specimens the spirotheca of the fifth volution to the maturity has a clearly discernible keriotheca, and the spirotheca of the third to the fourth, occasionally the fifth volution, appears to be composed of four layers resembling closely in structure the spirotheca of the genus Fusulinella MöLLER. This structure of the wall is clearly shown as fig. 25 on pl. 11 in his paper. Describing Triticites exculptus (1957, pp. 225-228, pl. 12, figs. 1-7, Text-figs. 2a and 2b) from the Hida Massif, IGO also pointed out that the spirotheca of this species was composed of the four layers in the inner three volutions.
In Triticites sp. A of SADA which was collected from the Onogahara Limestone of Ehime Prefecture, the spirotheca of the first to the fourth volution resembles that of Profusulinella consisting of a tectum and the upper and lower tectoria. Beyond the fifth volution the spiro-theca becomes a typical wall which is composed of a tectum and a distinct keriotheca. There are also many examples having the same spirothecal structure as that of Triticites sp. A. They are represented by the following species: Triticites montiparus of KANMERA (1958, p1. 25, fig. 22), T. cf. kagaharensis of IGO (1958, p. 235, pl. 15, fig. 3), etc. These three examples are also illustrated in this paper (See FIGS. 1-6 of PL. 23).
To sum up, in the spirothecal structure of the genus Triticites there are two types of T. secalicus and T. sp. A.

日本語

廣島大學理學部地學教室

[ISSN] 0073-2303

[NCID] AN00213676