226 Scientific Proceedings, Royal Dublin Society. 



(7) Few suckers (16-20) present = Spongeobrancliaea australis, d'Orb., 



8-22 mm. 

 Numerous suckers (ca. 280) present = Spongeobranchaea polycotyla, 1 



sp. n., 13 mm. 

 (2) Buccal cones present (8). 

 Buccal cones absent (9). 



(8) Kadular formula : 6 to 14-1-6 to 14 (10). 

 Baclular formula : 3-1-3 = Paraclione. 



Badular formula : 3-1-1-1-3 = Thalassopterus zancleus, Kwiet., larvae 

 1-2 mm. 



(10) Body broad in centre, more or less pigmented, head small = Clione 



limacina, Phipps, 10 mm. 

 Body slender, unpigmented, head large = Clione gracilis, 2 Massy, 

 10 mm. 



(9) Jaw a single row of small spines (11). 



Jaw a double or triple row of sma\l spines ; anterior tentacles long 



and forked = Halopsyche. 

 Jaw (?) a group of small spines ; two unbranched nuchal tentacles 



exceeding the body in length = Clionopsis longicirrata, sp. n., 3 mm. 

 Jaw (and gills) absent. Hook- sacs very large (12). 



(11) Radula having median tooth sickle-shaped with denticles ; a tetra- 



radiate posterior gill = Notobranchaea tetrabranchiata, Bonn., 



4-16 mm. 

 Badula having median tooth resembling that of Notobranchaea ; 



posterior gill a membranous ring = Fowlerina Hjortii, Bonn., 



5-9 mm. 

 Badula having median tooth sickle-shaped without denticles ; a 



tetraradiate posterior gill = Microdonta longicollis, Bonn., 7 mm. 



(12) Badula having median tooth triangular with many denticles = C'epha- 



lobrachia macrochaeta, Bonn., 5-10 mm. 

 Radula having median tooth with straight margin and few denticles 



= Ceplbalobrachia Bonnevii, sp. n., 2-50 mm. 

 Radula having median tooth with a median projection, no denticles 



and up-turned shovel-like ends = Thliptodon atlanticus, sp. n., 



3-7 mm. 

 Radula having median tooth crescentie, relatively large and with 



many denticles = Thliptodon rotimdatus, sp. n., 3-4 mm. 



1 The number of sucker-bearing appendages was not ascertained. <S. australis, the 

 only other species of the genus yet known, has two lateral arras. 



2 Perhaps only a variety of G. limacina. 



