. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 140 TERRESTRIAL AIR-BREATHING MOLLUSKS. are arranged in straight transverse rows, the marginals in oblique rows, as acu- leate marginal teeth always are. This tendency to obliquity in the rows of aculeate teeth we have seen most plainly shown in Glandina. To show the general arrangement of the teeth in straight and oblique rows I repeat the fig- ure by Morse in " Land and Fresh-Water Shells, N". ; I., which was probably drawn from L. agrestis. It must be borne in mind that this figure is not intended
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 140 TERRESTRIAL AIR-BREATHING MOLLUSKS. are arranged in straight transverse rows, the marginals in oblique rows, as acu- leate marginal teeth always are. This tendency to obliquity in the rows of aculeate teeth we have seen most plainly shown in Glandina. To show the general arrangement of the teeth in straight and oblique rows I repeat the fig- ure by Morse in " Land and Fresh-Water Shells, N". ; I., which was probably drawn from L. agrestis. It must be borne in mind that this figure is not intended to show the character* of the separate teeth, for which I refer to my plate. The genus Limax differs from Zonites in its dentition by having more slen- der, spine-like marginals, instead of the short, strictly aculeate form. The base of attachment of the marginals in Limax is also different, being less sole-like and more irregularly'eireular on the extreme marginals. Another difference is Fig Lingual DeDtition of Limax. that the marginal teeth do not increase in size so rapidly, and then decrease gradually as they pass off laterally, thus giving an irregularly crescentic form to each half of every transverse row. In L. maximus the marginal teeth de- crease gradually in size from the first to the last. It is the same with agrestis, but I believe the character is not generic, as L. montanus differs in this respect. It will be seen that even in the few species existing in North America there is considerable variation in the lingual dentition, especially in the bifurcation or non-bifurcation of the marginal teeth, the development of the side cusps to the central and lateral teeth, and the presence or absence of distinct Cutting points to these cusps. I shall, however, simply describe the dentition of our species, without reference to the subgeneric or generic value of these differences of dentition, or of the peculiarities of the mantle on which also generic and sub- generic d
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