Our largest female and largest male have respective total lengths of 1013 (840 + 173) and 740 (575 + 165). Our smallest specimens, captured on September 9, measured 215 and 230 mm. in length of body, and probably represent young of the year. The snake found in hibernation on April 5 measured 275 in length of body. The ventrals of 11 males averaged 161.3 (158-171) and those of 14 females, 165.1 (160-170); subcaudals of eight males averaged 69.6 (66-74) and those of 14 females, 61.5 (52-73).
Males seem to have small scales in the anal region that are more strongly keeled than scales elsewhere on the body (the scales catch on finger tips when rubbed in a posteroanterior direction), but males lack small tubercles on the upper and lateral parts of the head as mentioned by Maslin (1950:433). The comments of the same author (op. cit.:434) concerning integumental poison glands in the nuchal region of this species are of interest in view of several reports that we received of swollen extremities resulting from handling snakes of this species.
In using the generic names Rhabdophis and Amphiesma for species formerly placed in the genus Natrix, we follow Malnate (1960), who divided Natrix (auct.) into five distinct genera.
Amphiesma vibakari ruthveni (Van Denburgh)
Natrix vibakari ruthveni Van Denburgh, Proc. California Acad. Sci., ser. 4, 13(2):3, July 26, 1923 (type locality, Pusan, Korea).
Specimens examined (5).—Central National Forest, near Pup´yong-ni, 1 (KU); 4 mi. SW Ch´ongyang-ni, 1 (KU); 10 mi. NE Mosulp´o, Cheju Do, 1 (UMMZ); 6-7 mi. NNE Sogwi-ri, Cheju Do, 1 (KU), 1 (UMMZ).
Remarks.—The specimen from the Central National Forest was captured on August 18 near a stream on a damp ground-cover of leaves. The specimens from Cheju Do were taken in early September, one in a grassy area, and the other two on earthen banks of road-cuts on the slopes of Halla San. The stomach of one individual from Cheju Do contained an earthworm. Our largest specimen, a male having 154 ventrals and 68 subcaudals, measured 508 (380 + 128).
The subcaudal counts of 68 (KU 38861) and 69 (UMMZ 113461) on two males from Cheju Do are higher than the maximal count known for the subspecies ruthveni in Korea, and resemble those of Amphiesma vibakari vibakari of the Japanese islands. The subcaudals average 61 (55-65) in ruthveni and 71 (63-83) in vibakari
according to Van Denburgh (1923:3-4). A juvenile from the Central National Forest (KU 38862), lacking the tip of the tail, has 64 subcaudals.
Dinodon rufozonatum (Cantor)