Nomeus, Psenopsis, Ocycrius, Icticus, Ariomma, P. arg., P. ech., T. cuv. and T. atl. have a esophageal sac. The structure of the sacs and the teeth found in the sacs were examined with conventional anatomical and histological methods. An antiformin method was also used in the dissection of the sacs.
The esophageal sac-cavities like diverticula communicated with the esophagus. Two shapes of sacs were found. Ocycrius, Psenopsis, Icticus, Ariomma and Nomeus had kidney-shaped sacs and the sacs of P. arg., P. ech., T. cuv. and T. atl, were elliptical.The sac wall was protected with thick muscular layers, the inner was circular and outer was longitudinal. The sac mucosa contained a supporting bone or cartilage. The inner surface of the sac mucosa of Ocycrius, Psenopsis and Icticus appeared wrinkled. Mucosal surfaces of Ariomma, Nomeus, P. arg., P. ech., T. cuv. and T. atl, had polypoid processes. The supporting cartilage was only recognized in the polypoid processes of T. cuv. and T. atl., and showed some ramifications. No esophageal teeth were found in these two fishes. The other polypoids lined with supporting bones had bony basal pro-cesses in their bases. The supporting bones were attached to the muscles of the sac wall with basal processes. The basal processes showed two types of bases, one Nomeus, P. arg. and P. ech. had five or six radial processes, another Ariomma had a scale-like process. The supporting bones or cartilages were separated from each other.
Wrinkled mucosa also was lined with the supporting bone in the connective tissues under the epithelium.
Many tiny esophageal teeth were found in both the wrinkled and polypoid type mucosa excepting in the two fishes as mentioned above. Each tooth consisted of the homogeneous dentin and the pulp, but it was not clear whether they were covered with an enamel like substance. The tooth was fixed to the attachment bone by the supporting bone with a disc of connective tissue fibers (contact area).
(The authors wish to acknowledge to Dr. G. VAN HUYSEN, Professor of Anatomy, In-diana University School of Dentistry, and to Dr. T. ABE, Tokai Regional Fisheries Research Laboratory, Ministry of Agriculture and Forestry, for their suggestions.)