Dicrostonyx groenlandicus (Traill)
Figs. 3 and 4
Baculum: stalk elongate, greatest length (3.1 mm.) 2 1/5 to 2½ times greatest breadth, and 4½ times greatest depth; digitate processes usually cartilaginous, occasionally lateral processes partly ossified; basal tuberosities weakly to moderately developed, medially confluent; posterior profile in dorsal view rounded with rounded posterior apex or shallow notch; dorsal concavity in end-view shallower and not so wide as ventral concavity; median constriction approximately 2/3 greatest depth; ventral part of base in end-view wider than dorsal part; shaft straight or slightly curved; base of stalk placed dorsally relative to axis of shaft; stalk spatulate, sometimes with distal enlargement; at mid-point stalk wider than high; lateral profile in dorsal view sloping gradually without abrupt curvature anterior to point of greatest width.
The baculum of Dicrostonyx torquatus figured by Ognev (1948:476) agrees with that of D. groenlandicus in shape of stalk, and in lateral digitate processes that are small relative to size of median process; but differs in more elongate, terminally enlarged, bulbar shape of median process. None of my specimens showed ossification in the lateral processes, observed by Hamilton (1946:381) in Dicrostonyx rubricatus richardsoni [ = D. groenlandicus richardsoni]. In all of my specimens the cartilaginous median process was larger than that figured by Hamilton, or by Dearden (1958:542).
Specimens examined: Four from; Point Barrow, Alaska, 52524 (Barrow Village), 67264 (died in captivity); Brooks Range, Alaska, 50536 (Wahoo Lake, 69°08', 146°58'), 50539 (Porcupine Lake, 68°51'57", 146°29'50", 3140 ft.).