than previously thought, occurring from western Iceland and the Faroe Islands to the Hebrides, Scotland, and Ireland, to as far south as France and Western Sahara. This species is found on or near the bottom over the continental slope, in water deep. It has been reported from a depth of off Iceland, but the figure is confounded by taxonomic confusion. Description The maximum length of the mouse catshark has been variously reported as and . The larger figure comes from Iceland and is reflective of the aforementioned taxonomic confusion, as the specimen of P. jensenii described by Bjarni Sæmundsson was long. This species has a firm body with a rather long, blunt snout. The nostrils are divided by triangular flaps of skin in front. The eyes are horizontally oval and equipped with rudimentary nictitating membranes (protective third eyelids). A thin ridge is present beneath each eye, and a tiny spiracle behind. The large mouth forms a wide arch, and bears well-developed furrows at the corners. The teeth have a narrow central cusp and multiple lateral cusplets on either side. There are five pairs of gill slits. The first dorsal fin has a rounded tip and is positioned over the aft portion of the pelvic fins. The second dorsal fin is similar in size and shape as the first, and is positioned over the aft portion of the anal fin. The pectoral fins are large and broad. The pelvic fins are distinctive, being large and wide with an evenly rounded margin. In adult males, the inner margins of the pelvic fins are fused together to form an "apron" partially covering the claspers. The anal fin is large and angular; its base measures roughly 12–13% of the total length, much longer than the distance between the dorsal fins. The pelvic, anal, and caudal fins are all very close to each other. The caudal peduncle is cylindrical and the caudal fin is low, with a small lower lobe and a ventral notch near the tip of the upper lobe. The dermal denticles are small and overlapping; each has an arrowhead-shaped crown bearing a horizontal ridge and three marginal teeth. There is a prominent crest of enlarged denticles along the dorsal caudal fin margin. Unusually for the genus, there is also a similar denticle crest along the underside of the caudal peduncle, extending to the forward portion of the ventral caudal fin margin. This