(Alder & Hancock, 1843)
The length of the body may reach 11 mm; it is coloured greenish white, with the digestive gland showing green or brownish through the translucent skin, especially within the cerata, which are arranged in a latero-dorsal pattern of up to eight transverse rows. Each ceras is smooth and rounded at the tip. The anal opening is antero-dorsal, just behind the head. The rhinophores are inrolled.
This species lives and feeds upon the algae Codium tomentosum and Bryopsis plumosa . All records of P. dendritica have come from shallow water, with rare captures on the lower shore.
Distributed in NW Europe from Norway to the Mediterranean Sea (Distr. P. dendritica), New England to the Caribbean Sea; Japan; Australia; California.