Abstract
Snow crystals extended in the direction of the b-axis were observed in a temperature range from -8°C to -10°C at the summit of Mt. Teine. They had almost the skeleton structure and possessed double plates. Observing this type of snow crystals in different stages, it was considered that when a prism face develops abnormally in the direction of the b-axis, neighbouring two frames curve and approach to each other, and then are combined to a new frame extending in the direction.
The occurrence frequency of this type of crystals was about 2% in all snow crystals observed throughout 10 hours. This type of snow crystals was morphologically the same as Schaefer's flare crystals and Yamashita's trigonal dendrites except for a strange behaviour of frames.
It is considered that the abnormal growth towards the b-axis occurs when a prism face develops at a rate of more than twice of those of neighbouring prism faces. Snow crystals with the repeated growth of the b-axis were also observed. It is considered that the repeated growth of the b-axis was due to the bunching of growth layers.
