ZONITOIDES NITIDUS. 143 
The ALIMENTARY SYSTEM shows a long, slender, and black G:sorpHAGUS, with 
SALIVARY GLANDS on each side, but not united above, with long dark grey duets ; 
the somewhat ovate yellowish-brown CRoP is imbedded in the dark-brown LIVER or 
digestive gland, upon which the opaque white ramifications of the hepatie artery 
due, presumably, to lime, as in Arion, and quite as conspicuous, while the abrupt 
terminations of the smaller branches are just as striking. 
The MANDIBLE or jaw is areuate, and of the usual 
crescentic shape, of a deep amber colour, with several 
strongly marked longitudinal lines, parallel with the 
undulating upper margin; the upper margin shows a 
slight indentation in the centre, and distinctly recurved 
ends, the lower margin shows a distinet median beak or ms 
rostrum, from which the outline forms a bold curve to Fic. 194. —Jaw or mandible 
: : f Zonitoides nitidus X 10. 
the angle of the upper margin; behind there extends a  ° (0”itides nitidus x 10 
ne ang Marlfield, Tipperary, Rev. 
distinct but almost transparent elasma. A. H. Delap. aici 
The LINGUAL RIBBON is of the usual oblong shape, about one-and-a-half mill. 
long and a half mill. wide, and formed of about eighty transverse series of teeth in 
obliquely curved rows, each row composed of a symmetrical median tooth with a 
long and powerful mesocone and a strong ectocone at each side; the laterals are 
nine in number, and bicuspidate, the mesocone being flanked by a broad and 
sturdy ectocone ; the marginals are, according to Schepmann, about eighteen in 
number and simply aculeate, gradually diminishing in size at the margins of the 
membrane, 
The formula of a Dutch specimen from Rhoon, near Rotterdam, is given by 
Schepmann as 18+2+4+2448, and the number of transverse rows being about 
eighty gives a total of 4,400 teeth for the species. 
Mr. W. G. Binney gives the formula of an American specimen, sent by Dr. 
Showalter, from Baldwin co., Alabama, U.S.A., as 3°+$+443+42°. ‘ 
PAAR RRL LAN 
Fic. 195. Fic. 196. 
Fic. 195, —Representative denticles from a tranSverse row of the teeth of Zonitofdes nitidus (Miiller) 
from Rhoon near Rotterdam x 600 (after Schepmann). 
Fic. 196.—Representative median, lateral, and marginal teeth of Zonitoides nitidus, from B 
u aldwi 
co., Alabama, highly magnified (after W. G. Binney). mon 
Reproduction and Development.—Little is known of the details 
of reproduction and development, but congress probably takes place early 
in the year, as many loosely agglutinated egg clusters have been found 
at the beginning of March, and young of only two millimetres diameter 
have been observed at the end of August, while half-grown shells are most 
numerous in early December. 
That the period of congress is probably early in the year may be inferred 
from the fact that specimens examined up to and including May were 
usually furnished with the gypsobelum or love dart, while those examined 
in the later months were almost invariably deficient of this weapon. 
The eggs are sub-globular in shape, and possess a firm opaque-white 
shell ; they vary in size from 1} to 14 mill. in length and are about a 
millimetre broad. 
They are deposited singly or in small loosely agglutinated clusters, of 
four to six eggs each, chiefly during spring and early summer, but the 
period may extend to September, the total number of eggs varying from 
thirty to fifty; they are said to hatch in fifteen or sixteen days, the 
young snail becoming adult in about fourteen months. 
