BRITISH NUDIBRANCHIATE MOLLUSCA. 45 



Genus 6. POLYCERA, Cuvier. 



Body smooth or tuberculated. Cloak indistinct, forming a digitated veil, and a ridge 

 bearing a row of tubercles on each side of the back. Tentacles 2, laminated, non-retractile, 

 without sheaths. Branchial plumes non-retractile, with lateral appendages. 



Tongue rather narrow., with 12 to 16 plates, the 2 next the centre on each side large, bicuspid : 

 no central plate. Lateral corneous jaws. 



Section 1. Veil dilated into tentacular filaments ; branchial appendages linear, 1 on each side. 



1. P. quadrilineata, Mull. White, with lines of yellow tubercles, and sometimes spotted or striped 



with black and orange ; veil large, digitated ; branchial plumes 7 to 9, pinnate ; processes 

 all tipped with yellow. Length £ to § inch. PL 22, 



Section 2. Veil short, bilobed and tuberculated; branchial appendages tubercular, more 

 than one on each side. 



2. P. ocellata, A. and H. Greenish-black, with large, tubercular, yellowish-white spots ; veil tuber- 



culated, whitish, continued along the sides to the branchial appendages, which are lohated 

 and branched ; branchial plumes 5, bipinnate ; tentacles conical. Length \ inch. PI. 23. 



3. P. Lessonii, D'Orb. Green or yellowish, with yellow tubercles; veil short, with numerous yellow 



tubercles continued along the sides to the branchial appendages, which are much lobated and 

 yellow; branchial plumes 3, bipinnate; tentacles clavate. Length | inch. PL 24. 



Genus 7. ANCULA, Loven. 



Body smooth ; cloak obsolete, represented by a row of filaments on each side of the 

 branchiae. Tentacles 2, clavate, laminated, non-retractile, with styliform basal appendages. 

 Head produced at the sides into tentacular processes. 



Tongue narrow, with 4 spines, the 2 next the median line large and broad, luith the inner 

 margin denticulated : no central spine. A spinous buccal collar. 



1. A. cristata, Aid. White, with the processes tipped with yellow or orange; tentacular appendages 2 

 at the base of each tentacle ; branchial plumes 3, tripinnate ; branchial appendages 5 on each 

 side. Length I -inch. PL 25. 



Genus 8. IDALIA, Leuckart. 



Body smooth, convex ; with a small indistinct cloak, margined with filaments, longest in 

 front of the tentacles. Head much produced in front, plain, thick. Tentacles 2, linear, 

 laminated, non-retractile, without sheaths. Branchiae simply pinnate, non-retractile. Foot 

 large. 



Tongue narrow, with 4 spines, the 2 next the median line large : no central spine. A spinous 

 buccal collar. 

 Section 1 . Centre of the back with filaments. 



Lingual spines next the centre large, falcate, and smooth or minutely denticulated; lateral 

 spines short. Spinous collar complete. 



