IN his recent discussion of the sporadic beaked variant in spadefoot tadpoles of the Scaphiopus hammondi group in western United States, Turner (1952) has concluded that in the contours of the larval beaks (= mandibles) are not valid criteria for the separation of the three commonly recognized northern forms of the group, and that the structure of the beak does not change significantly between the approximately halfgrown larval stage and metamorphosis. Buccal dimorphism in larvae of western spadefoots has long been known and has been discussed briefly by several authors, of whom Turner appears to have been the first to treat the character on the basis of population samples from widely separated localities. The problem is somewhat more complicated than he has indicated, however, and it warrants much further study. Ideally, it should be worked out along with a thorough basic review of the systematics of the genus. The hammondi group is not yet adequately understood, and the broad overlap in the ranges of S. h. hammondi and S. h. bombifrons, as currently defined, is perhaps an important factor in the larval problem. The present paper reviews the background of the problem and discusses some of the lines of investigation that may help to provide a satisfactory solution. Gilmore (1924) described dimorphic spadefoot larvae, referred to S. hammondi bombifrons, from the vicinity of Colorado Springs, Colorado. The larvae with hypertrophied mouthparts had markedly carnivorous habits. The beaks of these individuals were enlarged and thickened, the upper bearing a strong median cusp and the lower a pair of such structures separated by a deep notch. The jaw muscles were greatly enlarged, conspicuously modifying the contours of the head. This locality is near the Colorado limit of bombifrons, which is predominantly a Great Plains form, and is near the zone in which the ranges of bombifrons and hammondi are currently understood to meet or overlap (Turner, 1952, fig. 2; Wright and Wright, 1949, map 6; Stebbins, 1951, pl. 55). Smith (1934) quoted extensively from Gilmore, and described and figured the strongly cusped mouthparts of a carnivorous type of tadpole collected near Grant, Valencia County, New Mexico. No mention was made of the jaw musculature, but it was noted that the larvae had small partially devoured tadpoles in their mouths, when collected. Smith contrasted these carnivorous larvae with specimens referred to typical hammondi by Storer (1925) and by Wright (1929), and concluded that the differences are so marked that there