A 
MONOGRAPH 
OF THE 
LAND AND FRESHWATER MOLLUSCA 
OF THE 
BRITISH ISLES. 
Poyvtum MOLLUSCA Cuvier. 
Malacozoa, Blainville; Palliata, Latreille; Heterogangliata, Owen; Otocardes, Haeckel ; 
2 fa ~ . . ? ’ , 
Saccata, Hyatt ; Tetraneura, Schimkewitsch). 
‘The Mollusea (mollis, soft) are animals with soft and fleshy bodies, covered 
by ciliated epithelium, containing numerous interspersed cells which abun- 
dantly secrete the mucus which is so characteristic a feature of the group 
and gives the body its suppleness and viscosity. 
They possess a cephalic region in which are located most of the organs 
of special sense, a pallial region which develops or secretes the shell, and a 
pedal or ventral region which constitutes the locomotory organ. 
Internally they present distinct digestive, coelomic and circulatory cavl- 
ties and scattered nerve centres, and primitively were bilaterally symmetrical 
in their organization. 
Crass GASTROPODA Cuvier. 
(Paracephalophora, Blainville ; Cephalophora, Macalister ; Glossophora, pars, Lankester ; 
Cephala, Reeve ; Univalvia, Fischer). 
The Gastropods (yao77p, stomach; 705— foot) are the most typical of the 
molluscan phylum, possessing the distinctive characteristics of the eroup in 
the greatest degree and showing the least affinity to other phyla. 
heir chief features are a ventral and sole-like reptatory foot; a distinct 
head; a well-developed odontophore, armed with numerous transverse rows 
of recurved teeth; a hollow and more or less conical shell which may be 
spirally coiled and external, or reduced to the merest vestige and concealed 
within the tissues. 
SuBs-Ciass A NISOPLE URA lLankester. 
(Gastropoda, Pelseneer ; Platycochlides, Ihering). 
The Anisopleura (a, not ; tos, equal ; wAebdpd, sides) are characterized by 
the asymmetry of their organization, due to the torsion and semi-rotation the 
visceral sac has undergone, which has transferred the respiratory and excre- 
tory organs from their, original posterior position to an anterior and lateral 
one, and also led to the diminution or even complete atrophy and loss 
the primitively left auricle, the left kidney, and the left moiety of other of 
the paired organs of the body. 
Orper KUTHYNEURA Lankester. 
(Platymalakia, von Ihering ; Pulmonata, Fischer ; Moncecia, Troschel; Adelapneumona, Gray ; 
Pulmonifera Inoperculata, Woodward ; Inoperculata, Reeve ; Saccobranchia, setae 
The Euthyneura (cts, straight ; vetpor, a nerve or tendon) embrace those 
land, freshwater, and marine castropods i in which the twisting of the visceral 
nerve-ring, characterizing the Streptoneura, has become obliterated by the 
partial detorsion the visceral sac has since undergone, and is also noticeah 
29/3/02 
