EASTERN PROVINCE — INTERIOR REGION SPECIES. 



238 



rio. 255. 



Jaw of Umax. 



near and immediately behind the right eye-peduncle. (See Fig. 257 

 below, on p. 237.) 



Testaceous rudiment thin, concentrical, not spiral, covered above 

 with a thin and transparent periostraca, below smooth. 



Jaw arcuate, with slightly attenuated but blunt ends ; 

 anterior surface smooth; cutting margin with a decided 

 beak-like median projection. There is often a central 

 vertical carina to the jaw. The ends are often more 

 pointed than in the jaw figured. I have examined the jaw of all our 

 species. 



The dentition of Limax is nearly allied to that of Zonites. The lateral 

 teeth are arranged in straight, transverse rows, the marginals in oblique 

 rows, as aculeate marginal teeth always are. This tendency to obliquity 

 in the rows of aculeate teeth we have seen most plainly shown in Gland- 

 ina. To show the general arrangement of the teeth in straight and ob- 

 lique rows I repeat the figure by Morse in Land and Fresh- Water Shells 

 N. A., I, which was probably drawn from L. agrestis. It must be 

 borne in mind that this figure is not intended to show the characters of 

 the separate teeth, for which I refer to my plates in Terr. Moll., Y. 



The genus Limax differs from Zonites in its dentition by having more 

 slender, 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 circular on the 



Fig. 256. 



Lingual dentition of Limax. 



extreme marginals. Another difference is 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 

 gradually decrease in size from the first to the last. It is the same with 

 agrestis, but I believe the character is not generic, as L. moritanus 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 



