suggested by the variation in size of frogs collected or observed in 1954. Of nine frogs obtained on May 29, five ranged in snout-vent length from 26 to 28, and four from 42 to 54. Three specimens collected on October 9 measured 39, 41, and 55, and two obtained on November 6 measured 25 and 37.

Rana nigromaculata Hallowell

Remarks.—Rana nigromaculata is the most abundant ranid in central Korea and, in a general way, the ecological equivalent of Rana pipiens in temperate North America. The species is associated with most aquatic habitats, from rocky streams to rice fields and large impoundments. In the vicinity of Seoul the din of large breeding congresses was heard more or less continuously from mid-April to mid-May. Large numbers of juveniles (approximately one inch long) were noticed first on July 8 and were present

thereafter for about three weeks, being commonest in standing water after heavy rains or during prolonged showers. These data and the different sizes of individuals collected at the same time suggest either variable growth or, more probably, an extensive breeding season. Our earliest and latest dates of collection are April 16 and October 7. The Korean name for "frog," most often applied to R. nigromaculata, sounds something like "keg-oh-ree." The call is a prolonged, raspy, staccato croak, sometimes with a rising inflection at the end.

In addition to the localities listed above, the species was observed 5 mi. W Kwangju and 3 mi. S Osan.

Despite a high degree of individual variation, Rana nigromaculata seemingly varies geographically as well; some subspecies probably should be recognized, but the species as a whole has never been thoroughly studied systematically. The division of R. nigromaculata into three subspecies by Schmidt (1927:563-567) was considered untenable by Fang and Chang (1931:95-98), and it has been regarded by most recent authors as a variable, monotypic species.

The named subspecies R. n. chosenica (Okada, 1931:89, with type locality at Seoul, and geographically restricted to Korea) was considered a subspecies of Rana plancyi by Shannon (1956:36). The most trenchant characters of plancyi seem to be the wide dorsolateral folds, the uniform greenish dorsum, the presence of dermal pustules on the back between the dorsolateral folds, and the lack of a mottled pattern on the posterior surface of the thigh. Among our specimens of R. nigromaculata, the width of the dorsolateral folds is variable, a uniform greenish dorsum is found only in large males, dermal pustules are mixed with ridges in only one male (KU 38733), and all have a spotted or mottled pattern on the posterior surface of the thigh. All of our specimens having an indistinct pattern on the back, or lacking a pattern, are males and resemble the photographs of males published by Moriya (1954: pl. I, fig. 5) and Liu (1936: pl. IV, figs. 1-2); juveniles of both sexes and large females have contrasting patterns.

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

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.

In our specimens, R. amurensis coreana differs from R. temporaria dybowskii in having (1) smaller maximal size, (2) more slender body, (3) shorter legs, (4) incompletely webbed toes, (5) no mottling or barring on lips, (6) no contrasting barred pattern on hind legs, (7) dark brown stripes (usually) between