Tadpoles.—Tadpoles of this species have been found in weed-choked ponds in eastern Panamá Province. The following description is based on KU 104097, a specimen in developmental stage 34 (Gosner, 1960).

Total length, 20.5 mm.; body length, 8.2 mm.; body slightly wider than deep; snout pointed; nostrils large, situated dorsally, much closer to snout than eyes, directed anteriorly; eyes moderately small, situated dorsolaterally and directed laterally; spiracle sinistral, located just posteroventral to eye; anal tube dextral. Tail xiphicercal; caudal musculature moderately deep, becoming slender posteriorly, extending beyond caudal fin; fins deepest at about one-third distance from body to tip of tail; dorsal fin extending onto body, deeper than deepest part of caudal musculature; ventral fin slightly shallower than musculature. Mouth small, terminal, lacking teeth and fringing papillae, but having finely serrate beaks. In preservative, top of head pale brown; dark stripe from tip of snout through eye to posterior edge of body, narrowing to thin line on proximal one-fourth of tail; venter white; tail creamy tan with fine black flecks most numerous posteriorly; posterior two-thirds of fins edged with black. In life, top of head yellowish tan; lateral stripe brown; belly white; anterior half of tail lacking pigment; posterior half deep orange; iris pale bronze ([Pl. 15]).

Remarks.—Evidence for intergradation of Hyla microcephala with H. underwoodi is provided by four specimens [USC 818 (2), 6081-2] from 6.1 kilometers northeast of the mouth of the Río Tarcoles, and nine specimens [USC 8254 (2), 8255, 8256 (4), 8258 (2)] from Parrita, both in Puntarenas Province, Costa Rica. These localities lie about two-thirds the distance from the northwesternmost locality for H. m. microcephala (Palmar Sur) to the southeasternmost locality for H. m. underwoodi (Barranca). Although in most aspects of coloration the frogs are more nearly like H. m. underwoodi than H. m. microcephala, some specimens have longitudinal lines on their shanks, such as are characteristic of H. m. microcephala. The dorsal pattern varies from nearly complete longitudinal lines to broken lines, fused into an X-shaped scapular mark or not.

As noted by Rivero (1961:135), Hyla microcephala seems to be closely related to Hyla misera Werner, a species having a wide distribution east of the Andes in South America. Despite the similarity in color pattern, size, and structure, we are reluctant to place the two taxa in the same species until data on coloration in life, mating calls, and life history are available for Hyla misera and compared with those of Hyla microcephala.

The status of Cope's Hyla cherrei is questionable. Since the type, the only specimen ever referred to the species, apparently is lost, the only extant information regarding the taxon is contained in the original description (Cope, 1894). There the species was characterized as having a narrow dorsolateral white stripe and lacking pigment on the upper arms and thighs. These characteristics of the color pattern combined with the statements "vomerine teeth few, opposite the middle of the very large choanae" and "tympanic drum distinct, one half the area of eye" serve to distinguish H. cherrei from all other Costa Rican hylids, except H. m. microcephala and H. m. underwoodi. No statements in the type description will definitely associate cherrei with one or the other of these subspecies. Since it seems obvious that H. cherrei can be associated with H. microcephala, we prefer to place the name in the synonymy of the nominate subspecies, thereby preserving the commonly used name H. underwoodi (Boulenger, 1899) as a subspecies of H. microcephala.

Distribution.—Hyla microcephala microcephala inhabits coastal lowlands from the area of Golfo Dulce (apparently absent from the Osa Peninsula) in southeastern Costa Rica eastward in Panamá, including the Azuero Peninsula to northern Colombia and thence southward in the valleys of the Río Cauca and Río Magdalena in Colombia ([Fig. 1]). Except for the central area of the Canal Zone the subspecies is unknown from the Caribbean drainage in Central America, but in Colombia the subspecies occurs only in the Caribbean drainage. In Central America this frog occurs mostly on the coastal lowlands; the highest recorded elevation is 560 meters at El Valle, Coclé, Panamá. Throughout most of its range Hyla microcephala microcephala occurs in disturbed habitats—cut-over forests, secondary growth, and pastureland. It does not seem to be an inhabitant of either primary forest or of Curatella-savanna.

Specimens examined.—522, as follows: Costa Rica: Puntarenas: Golfito, KU 32172-207; 3 km. E Golfito, KU 86399, USC 2757-8; Palmar Sur, KU 64591-608, USC 2650 (14), UU 3907-32; *1.5-2.5 km. ESE Palmar Sur, KU 68293-7 (skeletons), 93957-62; Parrita, USC 8254 (2), 8255, 8256 (4), 8258 (2) [intergrades with H. m. underwoodi]; 3 km. NW Piedras Blancas, KU 103689; 6.1 km. NE mouth of Río Tárcoles, USC 818 (2), 6081-2 [intergrades with H. m. underwoodi]; Villa Neilly, USC 2651; *1-5 km. WNW Villa Neilly, USC 6182-4, 8003 (4), 8031 (3), 8032; *10.5 km. WNW Villa Neilly, KU 64609-27, 68398 (eggs).

Panama: Canal Zone: Albrook Air Base, TNHC 23389, 23497; Balboa, ANSP 19555-6; *Fort Clayton, UIMNH 42008-12; *2.8 km. SW Fort Kobbe, KU 96015-25; *Frijoles, MCZ 19208; *Bamboa, MCZ 21507; *8.3 km. N Gatún Locks, TNHC 23441; *Juan Diaz, MCZ 13747; *Juan Mina, AMNH 55436-7, ANSP 21811-2, UMMZ 126734, 126735 (6), UU 3900-6; *8-14 km. N Miraflores Locks, TNHC 23374-88, 23390-409, 23411-38, 23440, 23442-60, 23462-76; 23478-83, 23492, 23555-60, 23562-76; *Río Chagres, AMNH 55430, 55439; *Río Cocolí, 3.5 km. N Miraflores Locks, TNHC 23410; *Summit, ANSP 23365-71, FMNH 22966-9, KU 97783-87. Chiriqui: 5.5 km. E Concepción, AMNH 69772; *14.4 km. E Concepción, AMNH 69773-8; 2 km. S David, AMNH 69779; *Progreso, UMMZ 58252, 58253 (2), 58254, 58436; Río Gariché, 8.3 km. ESE Paso Canoas, KU 103065-8. Coclé: 1 km. SE El Caño, KU 103042-51; El Valle de Antón, AMNH 59614-18 (10), 69785, ANSP 23502-5, KU 77201-14, MVZ 66578-83, UIMNH 46532. Colón: Cement Plant, Transisthmian Highway, FMNH 60394-5. Darién: El Real, KU 80454-5, 103052-64, UMMZ 125036 (10), USNM 140567-8; Río Canclon at Río Chucunaque, UMMZ 125035; *Río Chucunaque, near Yavisa, AMNH 59523. Los Santos: Tonosí, KU 101606-9. Panamá: 5 km. S Bejuco, AMNH 69782; 3 km. W Chepo, KU 77172-4, 104097-8 (tadpoles); *6 km. WSW Chepo, KU 77175; *Chico, Río La Jagua, USNM 129070; *La Joya, Cacora, ANSP 25129-33; Madden Dam, FMNH 67819; Nueva Gorgona, AMNH 69780-1; *1.6 km. W Nueva Gorgona, AMNH 69783-4; 1.5 km. W Pacora, 77176-200; *Río La Laja, near Chamé, ANSP 21845; *Río Tapia, MCZ 10048; *Tapia, AMNH 18930, 18950, 18952-3; *18 km. E Tocumen, MVZ 78662.

Colombia: Chocó: Sautatá, Atrato, FMNH 74918 (2), 74919. Magdalena: Aracataca, ANSP 19755-7; Curumani, MCZ 21465-74, UIMNH 28855; UMMZ 90168, USNM 118247; El Banco, Río Magdalena, ANSP 25061; Fundación, UMMZ 48281-2. Tolima: Espinal, MCZ 15068; Mariquita, FMNH 81822-3. Valle: Sevilla, MCZ 13751-3.

Hyla microcephala underwoodi Boulenger