832 THE YOUNG 



of the purest white, without the slightest 

 trace of stain which so often disfigures carded 

 specimens. — Eds.] 



CONCKOLOGY. 



LAND AND FRESH-WATV.R SHELLS. 

 By H. T. Robson, Stocktoi-on-Tees. 

 ( Continued from page 311 .) 



Genus, Balea. 

 We have here another genus, containing 

 one species only, in which the animal closely 

 resembles that of Bulimus ; the shell is, how- 

 ever, coiled the reverse way like Clausilia, 

 but without the clausilium which the shells of 

 the latter possess. The species is named 

 Perversa. 



Perversa. — The shell is small and 

 conical, thin and horny, resembling that of 

 Bulimus in form, but coiled in the opposite 

 direction, the aperture is small and without 

 internal teeth ; there is ,1 very minute 

 umbilicus. It is found in crevices of walls 

 and trees, among moss, &c. 



Genus, Pupa. 



This geuus, which has received its name 

 from the resemblance of the shell to the pupa 

 or chrysalis of an insect, has a cylindrical 

 shell rounded at the base and with rounded 

 spire composed of many whoris, with a small 

 umbilicus, generally with tech in the aper- 

 ture. The animal is shorn, with short 

 tentacles, the lower pair being very short. 

 The species are Secale, Muscori.m, C ylindracea, 

 and Anglica. 



Secale. — This, the largest of the genus, has 

 a shell about a third of an inch in length, 

 with the spire rather more pr inted than it is 

 in the other species, of a brownish color, 

 aperture with seven internal teeth. Found 

 chiefly in the South-west of E lgland m chalk 

 districts. 



Muscorum. — This is smaller and more 

 oval in form than the last, bright and trans- 

 parent, the aperture is small and without 

 teeth. It is found among moss and under 



NATURALIST. 



stones, 



Cylindracea. -This is still smaller than 

 the preceeding, being scarcely a sixth of an 

 inch in length, it is short and oval, trans- 

 parent, aperture with one internal tooth. 

 This is the commonest of the genus, and may 

 be found alljover the country, dwelling under 

 the bark of trees, about walls, under stones, 

 &c. 



Anglica. — This is about the same size as 

 the last, and of similar form, the aperture is 

 triangular and contains three well defined 

 and two less distinct teeth. It is found under 

 stones, dead leaves, and moss. 



Genus, Vertigo. 

 The shells of this genus are all very minute, 

 and require the magnifying glass for their 

 examination, the largest of them being only 

 an eighth of an inch in length ; they resemble 

 those oiPupa, but have mostly fewer whorls, 

 and are shorter in proportion to their 

 breadth : some of the species have the whorls 

 reversed. The animal is distinguished by the 

 absence of the lower pair of tentacles, the 

 upper pair are short. They are all found in 

 damp situations. The species are Antivertigo, 

 Moulinsiana, Pygmaa, Alpestris, Striata, Pusilla, 

 Vertigo, Edentula, and Minuta. 



Antivertigo. — A very small oval shell, 

 smooth and transparent, the aperture is 

 furnised with a number of teeth, sometimes 

 nine, sometimes not more than six. They 

 are found on plants growing in marshy places. 



Moulinsiana. — A doubtful British 

 species, a little larger than the last, with the 

 spire rather more pointed, yellowish, with 

 four teeth in the aperture. Living about 

 marshy places, under stones. 



Pygmsea. — A very small species, oval, 

 with rounded spire, brownish, smooth and 

 shiny, aperture with four or five teeth. This 

 is the commonest of the genus, and may be 

 found under stones, &c, in damp places. 



Alpestris. — -Similar to the last, and 

 supposed by some Conchologists to be only a 

 variety of it, the animal is paler in color, and 

 the shell a little narrower. It is found on 



