152 PUPILLA. 



Genus PUPILLA Leach. 



Pupilla Leach in TURTON, Man. Land and Freshwater 

 SheUs of the British Islands, 1831, p. 99. GRAY, P. Z. S., 

 1847, p. 176 (type P. muscorum). HERRMANNSEN, Ind. Gen. 

 Malac., ii, p. 362 (typus: Pupa muscorum L.). COCKERELL, 

 Nautilus, xviii, 1905, p. 104. Torquatella HELD, Isis, 1837, p. 

 919, for P. muscorum L. and P. triplicate Studer. HERR- 

 MANNSEN, Ind. Gen. Malac., ii, p. 583, "typus P. muscorum 

 L." Pupa of most authors. 



The shell is cylindric with rounded, obtuse ends, rimate 

 and often perforate, of short, slowly increasing whorls, the 

 sutures but slightly oblique. The small aperture has 0-5 

 teeth, the parietal, columellar and palatals deeply placed 

 when present ; no basal fold and no teeth in immature stages, 

 Peristome reflected narrowly. Shell axis small, perforate. 



The foot is about half as long as the shell, skin nearly 

 smooth. Inferior tentacles short but distinct. Shell carried 

 with the spire slanting upward a little. Some species at least 

 are ovoviviparous. 



Type: P. muscorum (L.). Distribution: North America, 

 Eurasia, Africa, Australia, almost wholly in temperate and 

 cold regions. They are ground snails, living under wood and 

 stones and among leaves in moderately humid situations. 



Pupilla is a widely distributed group, nowhere numerous- 

 in species, but generally abundant in individuals. The species 

 are among the most variable of their family in size, color, the 

 number and size of teeth and development of an external 

 crest features usually serving for specific definition. Albino 

 shells are not uncommon ; sometimes they form a considerable 

 part of the colony. Shortness is a more frequent variation 

 in nearly all species which have been collected in quantity. 

 Whether this quality is an inherited strain or due to early 

 formation of a lip in individuals born late in the season has 

 not been ascertained, as no breeding experiment has been car- 

 ried out. It is clear, however, that some colonies of P. mus- 

 corum comprise short and long shells, and those with one, 

 two, or with no teeth, and are doubtless hybrid complexes. 

 Similar conditions are found in some other species. 



