498 MOLLUSCA SUB-KINGDOM VI 
Punctinae. Jaw of numerous separate plates; shell minute. Includes the 
Holaretic genera Punctum, Morse, and Sphyradiwm, Charp., and the New Zealand 
genus Laoma, Gray. Recent. 
Endodontinae. Jaw-plates united more or less completely. Genera: Pyramidula, 
Fitz. Discoidal or low conic, with tubular ribbed whorls and open umbilicus. Car- 
boniferous to Recent. This is one of the most ancient land Mollusks known, and is 
the oldest Helicoid form. Phasis, Amphidoxa, Flammulina, and Endodonta, Alb., are 
sunilar austral forms, but are only known Recent. 
Family 4. Arionidae. 
Slugs having the shell reduced to a flat plate or a few granules, nearly or entirely 
concealed, or absent. Mantle in the form of a shield on anterior part of the body; teeth 
of the quadrate type. Recent. 
This family is probably derived from the Endodontidae by degeneration of the 
shell. Arion, Fér., and Anadenus, Heyn., are leading genera of Europe and Asia ; 
Ariolimaz, Morch., and Prophysaon, Bland, those of North America. 
Family 5. Philomycidae. 
Slugs somewhat similar to Arionidae, but the mantle covers the entire upper surface 
of the body. A shell is completely absent ; hence no fossil forms are known. 
Superfamily 4. ELASMOGNATHA. Morch. 
Jaw with a strong squarish process of attachment above. 

Family 1. Succineidae. 
Fic. 1048. Shell thin, ovate, consisting of few whorls. 
Succinea peregrina, ; . ayes 5 ql 3 
abe cee AGG: Succinea, Pfeiffer (Fig. 1048). Shell thin, ovate, amber-coloured, 
ae Tuchoritz, translucent, with short spire, and large body whorl. Outer margin 
ohemia. ; 3 3 : : 
of aperture sharp. Tertiary and Recent ; abundant in the Loess. 
Range and Distribution of the Gastropoda. 
Of all classes of Mollusks, the Gastropods exhibit the most manifold 
variety. Beginning in the Cambrian, they acquire a very gradual increase 
and distribution, and are at present enjoying their maximum vigour. There 
exist probably over 20,000 recent species, about three-fifths of which have 
gills, the remainder being air-breathers. 
At the base of the Cambrian (Olenellus zone) are found such archaic 
genera as Scenella, Stenotheca, Platyceras, Rhaphistoma, Pleurotomaria, and a 
number of doubtful Pteropod-like forms (/Zyolithes, Hyolithellus, Salterella, Torel- 
lella, ete.), which evince the great antiquity of the Aspidobranchs and forms 
resembling the Capulidae. In the later Cambrian the Lhipidoglossa (represented 
by the Plewrotomariidae, Euomphalidae, and Bellerophontidae) predominate ; and 
associated with these are certain Pteropod remains, members of the Capulidae, 
and «a few genera probably referable to the Turbinidae. A notable genus 
occurring here is Subulites, which bears some resemblance to the Pyramidellidae, 
and exhibits a distinct channelling at the base of the columella. 
Unfortunately the poorly preserved remains of Cambrian Gastropods afford 
