PLEUROBRANCHUS. 13 



on many parts of our eastern and western coasts from 

 Berwick and the Hebrides to Guernsey; Dublin Bay 

 (Kinahan); Bantry (Norman); Malbay, co. Clare (Har- 

 vey): local and not common. It appears to have an 

 extensive range in the European Seas, from Bohuslan 

 in Sweden (Loven), along the northern and western 

 shores of France, and on both sides of the Mediterranean, 

 as well as in the Adriatic, to the iEgean (Forbes), at 

 depths varying from 27 to 40 f. 



" When first taken, the animal creeps quickly and 

 with great vivacity" (Clark). "Like the land-slug, it 

 progresses by obscure undulatory motions of the foot ; 

 but it justly claims the f bad preeminence' of being 

 superior in sluggishness and tardiness" (Johnston). 

 According to Lacaze-Duthiers it does not shun the 

 light when placed in captivity, and it often comes to 

 the surface of the water; if disturbed it contracts and 

 rolls itself into a ball, or closely and strongly adheres 

 by the foot ; it approaches the shore to deposit its 

 spawn, which is formed in ribbon-like and spirally 

 arranged masses (resembliag those of Doris), several of 

 these masses being deposited by the same individual. 

 He supposes the tentacles are olfactory organs, as Han- 

 cock believed is the case with the Bullidae. In the 

 mantle, foot, and gill-plume of P. plumula Dr. Johnston 

 detected " many small crystalline spicules of carbonate 

 of lime : these are colourless, short, cylindrical, and 

 rounded at both ends;" and they are irregularly dis- 

 posed, as in the Doris family. He says the present 

 species feeds on seaweeds. The buccal or maxillar 

 plates are large and regularly reticulated, like the com- 

 pound eyes of certain insects. Mr. Jabez Hogg likens 

 the odontophore to that of some Pulmoniferous mol- 

 lusks, and he describes the dentition thus : — " Median 



