Habitus: Length: 4.5-5 mm, width: 2-2.5 mm. The body is elongate with rounded front and hind end. The head region is not delimited from the rest of the body through a constriction. Maximum width is at the front end; towards the hind end the body gradually narrows but never measures less than 2 mm in breadth.
The dorsal surface is dark olive-green, being paler dorsally to the pharynx and the copulatory apparatus; the ventral surface is white. Two small, kidney-shaped eyes are situated in small yellowish spots.
The anterior ramus gives rise to a pair of preocellar diverticula and behind the eyes it gives off 15-19 lateral diverticula on either side of the body. The lateral diverticula are moderately branched.
The testes are distributed irregularly between the intestinal branches. The penis shows a broad basal section, the bulb, and an arched distal portion. The vasa deferentia penetrate the penis bulb separately and open into an intrabulbar seminal vesicle, which is divided into two sections by a thin partition [probably this part of the description must be interpreted as that each of the two ducts expands to form an accessory seminal vesicle].
With respect to the female reproductive system, the ovaries and oviducts are very similar to those of other marine triclads. The oviducts run closely to the ventral nerve cords and unite to form a "common oviduct", which meets the bursal canal. The copulatory bursa is rounded. According to Sabussow's figures shell glands would discharge their secretion into the ventral section of the bursal canal [probably cement glands ?]. In general, the copulatory apparatus of P. solowetzkianuswould be rather similar to that of P. lobata and P. littoralis.
Ecology and Distribution
The species has been collected from under stones on the beach of Solowetzk Island and from rocks of the Domasnayaya Gora (67 07'N 32 52'E), both in the White Sea.
The original publication was unavailable; the present account is based on Wilhelmi's summary and on that of Böhmig (1906).