The mongolism was first reported as Down's syndrome in 1866 . Later research findings by Lejeune , Böök  in 1959, Ford  in 1959 and Jacob  in 1959, established the etiology of mongolism as due to the abnormality of chromosomes. From a dental point of view, Brown , Benda , Dow , Cohen , and Johnson  have made contributions respectively. According to these investigators, high incidence of periodontal disturbances and low caries prevalence can be deemed as the characteristics of this hereditary malady. Brown  also observed a congenital missing of one or two teeth in high frequency. It is, however, very seldom that we find an investigation of this kind in dental realm in the domestic publication. Recently, we encountered a case of mongolism which presented a congenital missing of lower deciduous lateral incisors bilaterally and, at the same time, a supernumerary tooth existed in the region between upper left central and lateral incisors.
A coelacanth was presented by the French Government to Mr. SHORIKI for his efforts with the cultural exchange between Japan and France. It was his idea to first exhibit the fish to the general public at the Yomiuri park managed by him. However, he also hoped that the fish would be observed by Japanese ichthyologists. Therefore, his permission for the dissection was given to the ichthyologists providing they could dissect the coelacanth without injuring its external appearance. On July 2nd. 1967, the fish was dissected by several scholars. They consisted of specialists in morphology, neurology, paleontology, dentistry and so forth. To preserve the external appearance, the dissection was restricted mainly to the viscera. The authors of this report joined in the dissection and observed the dental system of the fish. No available study of the teeth and surrounding tissues of the coelacanth was found in the literature, excepting MILLOT and ANTHONY'S report . However, their descriptions of the dental structures were unsatisfactory. A jaw tooth and some gill teeth were studied with conventional histologic techniques presented in this report. The terminology used in this paper is shown in Fig. 1. Jaw and gill teeth of a coelacanth (Latimeria chalumnal) were studied by means of a conventional histologic method. The teeth of this fish consisted of orthodentin and pulp. The tooth ankylosed with an attachment bone at their base. The attachment bone consisted of a cellular bone which was joined by a dense connective tissue with the jaw bone or the bone of the gill arch. One could not find any enamel like substance of the dentin surface. However, historadiographs showed some surface hypermineralization. The dense connective tissue between the attachment bone and the jaw bone or the bone of the gill arch, resembled that of a suture. No evidence of replacement of lost teeth was revealed. It was concluded that the histological structure of the coelacanth's tooth comprised one of the steps in the evolution of the exoskeleton of the ostracoderm to the teeth and supporting structures of the bony and cartilagenous fishes. Acknowledgements-The authors appreciate very much the permission given by Mr. Matsutaro Shoriki for the use of a rare fish coelacanth, and we are also particularly indebted to Professor Grant Van Huysen, Indiana -University School of Dentistry and Dr. Tokiharu Abe, Tokai Regional Fisheries Research Laboratory, for many helpful suggestions.