NATURAL CLASSIFICATION OF THE OASTEEOPODA. 163 



a Bulla and a Strombus than between the latter and an Atlanta, 

 for example ; and in reference to the genus Fhorus, I find the fol- 

 lowing remarks in my note-book : — " The animal of Phorus is 

 strikingly suggestive of Atlanta or Oxygyrus, and it has been 

 remarked that the dentition closely resembles that of the Hete- 

 ropod (Mo'rch). I am strongly inclined to think that the Phoridce 

 will be found to form the connecting link between the Gastero- 

 poda proper and the Heteropods." To return to the subject from 

 this digression, it will be easy to see that Firola and Cerophora 

 are representatives in the two groups above given — that Carinaria 

 represents Gardiapoda, and Atlanta Oxygyrus. Now if we deal 

 with the monoecious Gasteropoda as a whole, we shall have the 

 results as given in the following Table : — 



Class GASTEROPODA. 



Division I. MONCECIA (sexes combined). 



Subdivision I. Lingual dentition typically pavemental *. 



Order I. Pneumonophora (lung-bearing, or respiring in air). 



Suborder 1. Pulmonata (with air-chamber only). 



« 

 A. Habit terrestrial. 

 Analogy of Shell-characters. Illustrative Genera. 



{absent Janella. 

 ("internal Aneitianaf. 

 present * ^ j partial Omalonyx. 



L i general or investing Succmea. 



f absent Megimatium. 



Shell ... \ I internal Umax. 



| present \ , ■, [partial Parmacella. 



[ [investing Helix. 



{absent Thilomycus. 

 f internal Viquesnellia. 

 present -j , , f partial Baudebardia. 



[ \ investing Vitrina. 



Suborder 2, Pulmobranchiata (having both an air-chamber and a ciliated 

 surface or branchia for respiration in water). 



B. Habit aquatic. 



(absent 



f internal 



present \ , , fpatelliform Ancyclus. 



|_ external \ spiral Limnaa. 



* In some instances apparently strap-like, by reduction of the members of 

 the pleura. 



t A bitentaculate slug, occurring in N. S. Wales and the New Hebrides,- de- 

 scribed by me in Ann. & Mag. Nat. Hist. 1856, ser. 2, vol. xviii. p. 38. 



