External: Thick-bodied; mantle less than 1/3 body length; variable coloration; light brown body with large brown to dark brown spots on body and concentrated on the center of the mantle; large dark blots on most of body except keel; darker sides, head, tentacles, and neck; thick-skinned; short, pale keel; 3-part sole with gray side sections and cream middle section; clear mucus, milky when perturbed (Wiktor 2000; Schütt 2010).
Internal: Oval, asymmetric internal shell; rounded penis; very large, flat conical simulator/sarcobelum inside penis, pigmented in adults; a small, bent, papillate gland slightly off the penis apex; muscular retractor on penis apex; short rectal caecum (Wiktor 2000; Schütt 2010).
Similar to D. subagreste, but the latter has no/few spots, black pigmentation on penis, and a branched penial retractor muscle (Wiktor 2000).
Juveniles: Reticulate pigmentation shows up on skin (Wiktor 2000).
To 30 mm long extended (Schütt 2010); to 23 mm long, mantle 7 mm long (Wiktor 2000).
Moist, deciduous and mixed forest, sometimes coniferous forests (Wiktor 2000).
Mature in autumn (Schütt 2010).