POLYCERA. 75 



each side of the back: dorsal tentacles laminated, non-retractile, 

 without sheaths : oral tentacles obsolete or indistinct : gills 

 plumose, non-retractile, with lateral appendages : odontophore 

 rather narrow, with 6 or more plates on each side, the two 

 next the centre large and bicuspid : jaws lateral and corneous. 



This genus is not numerous in species, most of those known 

 inhabiting the coasts of Europe ; one is found in North Ame- 

 rica, and one in Brazil. It is the Themisto of Oken. 



1. Polycera quadrilineata, Miiller. 



Boris quadrilineata, Mull. Zool. Dan. Prod. p. 229 ; A, & H. Brit. Kud. 

 Moll. fern. 1, pi. 22. 



Body nearly linear, tapering behind, smooth, white, occa- 

 sionally freckled with black, with several rows of yellow or 

 orange tubercles, four of which (two at the margin of the 

 cloak and two at the sides below) are most prominent : mantle 

 expanded into a veil in front with four (or sometimes six) 

 stout, linear, pointed filaments, tipped with yellow, and con- 

 tinued into a faint pallial ridge on each side of the back : dor- 

 sal tentacles subclavate, with the laminated portion yellow : 

 gills 7-9, simply pinnate, with a linear lateral appendage on 

 each side : all the processes are tipped with yellow or orange. 

 L. 0-75. 



Yar. a. With 4 black bands uniting the principal rows of 

 Yellow tubercles. 



Yar. b. With alternate stripes of black and scarlet-orange 

 covering the whole of the body. 



Habitat : On small seaweeds in rock-pools, between tide- 

 marks and in shallow water on all parts of the British coast ; 

 not uncommon. Yariety b was found in Salcombe Bay (Alder). 

 The species ranges from Norway to the Mediterranean. The 

 variety a is that originally described and figured by Miiller 

 under the name of Doris quadrilineata, and perhaps ought to 

 be considered the type of the species ; but it is less common 

 than the bandless form, to which Abildgaard subsequently 

 gave the name of D. cornuta, supposing it to be a distinct 

 species. They are, however, undoubtedly the same. 



This beautiful species is rather lively in its habits, and is 



e2 



