THE YOUNG NATUBALIST. 



351 



measuring about an inch across, the whorls 

 are large and rounded, closely striated, and 

 with occasional folds shewing stages of 

 growth the spire is sunk below the outer 

 whorls, the aperture is large ; the shell is 

 brown, or sometimes greenish or grey. The 

 animal is black, with long thread-like ten- 

 tacles. They inhabit canals, ponds, and 

 sluggish streams, in the eastern, south- 

 eastern, and midland counties of England. 



Albus. — This is a small white shell, only 

 about a quarter of an inch in diameter, horny 

 in appearance ; the spire is only slightly sunk 

 below the outer whorls ; it is slightly striated 

 longitudinally. The animal is grey or brown. 

 It is common all over the country in ponds, 

 streams, canals, &c. 



Glaber. — This shell is similar in shape to 

 the last, but smaller, and with the whorls 

 smooth, it is of a greyish color, horny, and 

 glossy. It may be found in ponds and 

 marshes, and is generally distributed through- 

 out the country. 



Crista. — A very minute shell, whitish, 

 horny, and transparent, it has a series of 

 oblique ringes on the outer portion of the 

 last whorl, the aperture is expanded like the 

 mouth of a trumpet. It is found in ponds 

 and sluggish streams in all parts of the 

 country. This species is known also by the 

 name of P. nautileus. 



Carinatus. — This is a larger shell, 

 measuring about half an inch across when 

 fully grown, it is very flat on the under side, 

 the spire is slightly sunk, it is pale horny, 

 polished, and striated, it has a ridge or keel 

 around the outer edge of the whorl towards 

 the under side. It may be found in sluggish 

 streams, marshes, ponds, &c, and is pretty 

 generally distributed. 



Complanatus. — This is a very similar 

 shell to the last, but it is scarcely so flat on 

 the under side, and the spire is less sunk ; the 

 keel is also lower down, or closer to the under 

 side of the whorl than in Carinatus, it is also 

 darker in color, being yellowish brown, and 

 it is not so smooth. It is a more abundant 



species than the last, and may be found all 

 over England and Ireland, in ponds, ditches, 

 marshes, streams, and canals. This is more 

 generally known as P. marginatus. 



Vortex. — This is a smaller shell, very 

 flat, the whorls increasing very slowly iu size, 

 and very closely coiled ; it is flat on the 

 under side, the spire being sunk on the upper 

 side, the whorls slope outwards from the 

 upper side, and the aperture is oblique, it is 

 of a brownish colar. It is found in ponds, 

 marshes, &c, in all parts of the country. 



Spirorbis. — A very similar shell to the 

 last, the principal differences being that it is 

 not so much sunk on the upper, nor so flat 

 on the under side, both sides being about 

 equally concave, the whorls do not slope so 

 much as in Vortex, and the aperture is not so 

 oblique. It is found in similar situations, 

 and is distributed throughout the country. 

 Coiltortus. — The shell of this species is 



, small, and has the whorls more closely coiled 

 than any other of the genus, it is of a pale 

 brownish color; the upper side is very flat, 

 but with the sutures distinct, the under side 

 has a large umbilicus, being much more sunk 



; than the majority of the shells in the genus, 

 the aperture is half-moon shaped. It is 

 found in ponds, marshes, &c, but is not so 

 common as some of the others. 



Fontanus. — This is also a very small 



! shell, it is flat with angular whorls, the upper 

 side has the spire slightly sunk, the under 

 side has an umbilicus, it is yellowish brown, 

 bright and transparent, the aperture is angu- 

 lar. It is found in streams and ponds 

 throughout the country. 



Nitidus- — This shell is rather like the 

 last, the whorls being angular, the spire 

 slightly sunk, and an umbilicus on the under 

 side ; the angle of the whorls is not however 

 so acute as in Fontanus, and it is distinguished 

 by three or four internal lamidse, which are 

 indicated externally by dark lines. It is 

 found chiefly in the south of England, in 

 ponds and ditches. 



(To be continued.) 



