_Definition._--Small hylids attaining a maximum snout-vent length of 27 mm. in males and 32 mm. in females; dorsum yellowish tan with brown markings; thighs uniformly yellow, vocal sac in breeding males yellow; snout truncate in lateral profile; tympanum distinct, usually slightly smaller than one-half diameter of eye; vocal sac single, median, subgular; fingers about one-third webbed; toes webbed nearly to bases of discs, except only to middle of antepenultimate or base of penultimate phalanx of fourth toe; tarsal fold weak; inner metatarsal tubercle low, flat, elliptical; axillary membrane present; pupil horizontally elliptical; palpebral membrane unmarked; cranial elements reduced in ossification; sphenethmoid small, short; frontoparietal fontanelle large; tegmen tympani not extensive; quadratojugal greatly reduced; anterior arm of squamosal extending only about one-fourth distance to maxillary; posterior arm of squamosal not having bony connection with proötic; nasals lacking maxillary processes; medial ramus of pterygoid not having bony attachment to proötic; maxillary, premaxilary, and prevomerine teeth present; palatine and parasphenoid teeth absent; Mentomeckelians ossified; tadpoles having xiphicercal tails with deep caudal fins and terminal mouth lacking teeth; mating call consisting of one primary note followed by a series of shorter secondary notes; haploid number of chromosomes, 15 (known only in _H. microcephala_ and _H. phlebodes_.) _Content._--As recognized here the _Hyla microcephala_ group contains four species, one having two subspecies. An alphabetical list of the specific and subspecific names that we consider to be applicable to the _Hyla microcephala_ group are listed below. Names Proposed Valid Names _Hyla cherrei_ Cope, 1894 ? = _H. m. microcephala_ _Hyla microcephala_ Cope, 1886 = _H. m. microcephala_ _Hyla microcephala_ Boulenger, 1898 (_nec_ Cope, 1886) = _H. microcephala underwoodi_ _Hyla microcephala martini_ Smith, 1951 = _H. microcephala underwoodi_ _Hyla microcephala sartori_ Smith, 1951 = _H. sartori_ _Hyla phlebodes_ Stejneger, 1906 = _H. phlebodes_ _Hyla robertmertensi_ Taylor, 1937 = _H. robertmertensi_ _Hyla underwoodi_ Boulenger, 1899 = _H. microcephala underwoodi_