None of our frogs seems, therefore, clearly referable to the species _plancyi_, although some characters are suggestive of _plancyi_. Moriya (_op. cit.:19_), who studied variation of _R. nigromaculata_ in Japan, noted that one of the most distinct populations there (_R. n. brevipoda_) resembled _Rana plancyi_. Ting (1939) discovered that _nigromaculata_ and _plancyi_ were cross-fertile and raised hybrid larvae through metamorphosis. Pope and Boring (1940) suggested hybridization between the two species in eastern China, and the above mentioned facts suggest to us the possibility of hybridization in other regions. =Rana amurensis coreana= Okada _Rana temporaria coreana_ Okada, Annot. Zool. Japon., 11:140 (footnote), July 25, 1927, _nomen nudum_. _Rana temporaria coreana_ Okada, Jour. Chosen Nat. Hist. Soc, 6:19, pl. 1, fig. 7, 1928 (type locality, Keijo [= Seoul], Korea). _Rana amurensis coreana_, Shannon, Herpetologica, 12:38, March 6, 1956. _Specimens examined_ (9).--Central National Forest, near Pup´yong-ni, 1 (KU); 2 mi. S Ch´orwon, 1 (KU); 4 mi. W Ch´ungju, 1 (KU); 1 mi. N Oho-ri, 1 (KU); 5 mi. ESE Seoul, 3 (KU); Yongp´yong, 2 (KU). _Remarks._--One individual of _R. a. coreana_ (KU 38698) and one of _Rana temporaria dybowskii_ (KU 38715) were collected on May 29 along a stream in the Central National Forest in association with _R. rugosa_ and _R. nigromaculata_. Specimens of _coreana_ from the vicinity of Seoul were found in rice fields. The earliest date of collection was April 13 at Yongp´yong. Our largest specimen of _coreana_ measured 47 in snout-vent length. Because _R. a. coreana_ and _Rana temporaria dybowskii_ are sympatric in central Korea and closely resemble one another, the two species were not distinguished in the field and the following observations may pertain to either (or both) species. Wood frogs were observed 2 mi. E Songdong-ni on July 12 in paddies (rice fields) along with individuals of _Hyla arborea_, _Rana rugosa_, and _Rana nigromaculata_. At Chip´o-ri on April 6, individuals (probably _R. t. dybowskii_) were seen in a seepage pool from an abandoned rice field; _R. nigromaculata_ also was seen there. Six or seven egg masses (some having small tadpoles) were observed in the shallow water, but it was not certain to which species the eggs belonged. Completely metamorphosed young (probably _R. a. coreana_) were first seen 1 mi. N Oho-ri on June 9. At Taehoesan-ni on November 12, several sluggish frogs were seen in a small pool that was covered by a thin layer of ice. On September 26 in the Central National Forest, many wood frogs of various sizes were observed. _R. amurensis_ and _R. temporaria_ probably have extended breeding seasons that correspond to those of _R. rugosa_ and _R. nigromaculata_. Judging from our observations, _amurensis_ prefers the proximity of water, whereas _temporaria_ may occur some distance from permanent water.