101 



families are aąuatic, and all but the genera Neritina and Navicellus 

 are truly marine. They all have vrell-developed gills, and the 

 greater part have a more or less developed lateral membrane on each 

 side of the body, furnished with three or more beards on its lower 

 surface, and almost all have the eyes placed on a more or less distinet 

 peduiicle at the outer side of the base of the tentacles, all characters 

 absent in Proserpina. But notwithstanding all these peculiarities, 

 I am inclined to arrange the family Proserpinidce (including Proser- 

 pina and Ceres) in the order Scutibranchia, section Raphidoglossa, 

 and to form a suborder for it under the name Pseudobranchia, in 

 the šame manner as the families Cydophoridce and Helicinidcs form 

 the suborder Phaneropneumona of the order Tiostriferce. 



It may be thus characterized : — 



Pseudobranchia. Gills vascular, branched on the inner surface 

 of the mantle ; body and shell spirai ; eyes sessile ; operculum none. 



The open respiratory cavity, the separate sexes and the form 

 of the teeth, preclude its being arranged with the Pulmonobran- 

 chiata, with which it has been hitherto placed on accomit of its 

 terrestrial mode of life ; but as our knowledge of the structure of 

 Mollusca extends, it is found that some Piilmonobranchiata are 

 marine, as SiphonariadeB and AmphibolidcE, in the šame manner as 

 the terrestrial Cydophoridce and Oligyradce are properly arranged 

 in the marine and fluviatile Rostrifera. The ProserpinadcB might 

 be arranged with the latter families, as was proposed before the 

 teeth were known ; but there can be little doubt that the animals 

 which have the very numerous rows of such peculiar-formed teeth 

 as the Raphidoglossa, mušt have very different habits and modes of 

 life from those which have only seven rows of nearly uniform teeth, 

 of the Tcenioglossa or Rostriferous Mollusca. 



And though the animal of the Proserpinadce diiFers from the 

 more typical Raphidoglossae, yet all the peculiarities, except the 

 vascular organs of respiration and terrestrial mode of life, are found 

 in some of the genera of the suborder. Thus the eyes of Fissurella 

 are sessile on the outer side of the base of the tentacle ; the whole 

 family of Neritinidce and some of the genera of FissurelladcB are 

 destitute of any lateral fringe or beards ; so that though these organs 

 are the usual characteristic of these animals, their absence is no 

 proof that the family does not belong to the group, especially -cvhen 

 we consider that the teeth have all the peculiarities, indeed, are per- 

 fectly typical in form with this well-marked and very peculiar tribe, 

 and very probably it may prove that many terrestrial Mollusca may 

 properly belong to the order. 



The lingual membrane elongate, broad, with numerous longi- 

 tudinal series of close-set teeth ; the centrai teeth in 1 1 longitudinal 

 series, 5 . 1 . 5 . the two outer teeth on each side being large and irre- 

 gular ; the lateral teeth are numerous, crowded, compressed, linear, 

 nearly equal, transparent, with recurved tip. 



In Ceres Salleana the lingual membrane is broad, elongate, with 

 close-set teeth. Teeth .00. 5. 1. 5.00. in numerous longitudinal 

 series ; the centrai tooth is oblong, with a smooth recurved tip, the 



