Old individuals in the field could not be distinguished from adults; hence any animals that appeared older, or more developed, than subadults were classified as adults. In _P. truei_, subadult pelage appears first on the lateral line or on the flanks; new pelage is ochraceous and contrasts markedly with the gray juvenal coat. In _P. maniculatus_, the subadult pelage contrasts less with the juvenal coat; the new pelage progresses from anterior to posterior over the body in the same manner as in _truei_, but replaces the juvenal coat in a less distinct manner than in _truei_. As a result, contrast often is lacking between juvenal and subadult pelages in _maniculatus_ making it difficult to assign an individual to one of these two age categories when examined in the field. In museum specimens, the subadult pelage is much more noticeable because it can be compared with the pelages of other specimens. The subadult pelage in _P. maniculatus_ is duller than the adult pelage: In _P. truei_ the subadult and adult pelages appear to have an equal sheen. In early winter, the postjuvenal pelage acquired by young individuals of _P. truei_ was thick and luxuriant and indistinguishable from the winter pelage of adults. My observations lead me to conclude that individuals born late in the breeding season molt from juvenal summer pelage directly into winter adult pelage. Technically, this new coat is the postjuvenal one, yet it cannot be distinguished as such after the molt is completed. ANOMALIES AND INJURIES Anatomical anomalies were rare in the individuals of _Peromyscus_ that I examined. When anomalies were found they were striking, principally because of their low rate of occurrence. One female of _P. truei_, born in captivity, had a congenital defect of the pinna of the right ear, noted on the fifteenth day after birth. Closer examination then and later revealed that the pinna was normal in all respects except that the tip was missing. The tip showed no evidence of injury. When the mouse was subadult, this defective pinna was approximately half as long as the normal pinna. The topmost part of the defective pinna was somewhat more constricted in circumference than the normal one. On September 11, 1963, a subadult male of _P. truei_ was captured that had five functional toes on its right front foot, the only one of more than 175 individuals caught and handled in the field that exhibited polydactyly. The front foot was examined closely in the field, but it could not be determined how or where the extra bones of the sixth toe articulated. _Peromyscus_ normally has four full-sized toes on each front foot, and a small inner toe hardly more than an enlarged tubercle, having no nail.