Deroceras (Deroceras) bistimulatum Wiktor, 2000  

External: Slender-bodied; (preserved:) cream-brown or gray-cream body, with slightly lighter sides; may have pigmented reticulations in the posterior mantle skin; mantle posterior edge at half point of body; thin skin with calcareous particles inside (Wiktor 2000).

Internal: Longish, irregular penis with a narrowed middle; two small appendices on penis apex; a gland with a single trunk and two branches further dividing between the appendices; vas deferens attaches at the base of an appendix; penial retractor muscle attaches between the two appendices; two stimulators in penis, one fan-shaped with a long, sharp part and the smaller stimulator low and "husk"-like, and both stimulators striated on both sides; small rectal caecum (Wiktor 2000). .