26 THE NAUTILUS. 



specimens the callous deposit on the columella is heavy, and where 

 it meets the labium above, it is very thick. This is well shown in 

 figs. 3 and 8 ; within the aperture the outer lip is bordered by a 

 lighter-colored or white zone. 



All mature specimens and many of the immature ones are more or 

 less covered with a deposit of calcareous matter, which is often so 

 thick as to mislead as to the form of the shell, see figs. 4 and 9. 



Individuals are very numerous in some places, and scattering ones 

 can be found almost anywhere in the river. The very young were 

 found where there was little or no current, on sand or mud bottom, 

 or on roots and plants at the water's edge ; older ones were common 

 on rocks or the river bed where the current was strong. 



At two places the alluvial soil, though above any indication of 

 high-water, contained large numbers of this species, reminding the 

 writer of the remains of Tulotoma magnified at places along the 

 Coosa river in Alabama. 



Figures 8 and 9 are from the stream of a spring, and are more 

 perfect in the spire than those from the river, fig. 8 has the deposit 

 all removed, and fig. 9 has enough removed to show the spire. Fig. 

 10 is not mature ; it will be seen that the heavy columellar callus is 

 not yet formed. Fig. 2 is an extra large one ; it and figs. 3 and 7 

 are more than usually inflated. Much smaller ones were found than 

 the one shown in fig. 5. 



DESCRIPTIONS OF NEW MEXICAN LAND SHELLS. 



BT HENRY A. PILSBRY. 



A full account of the mollusks collected by Mr. A. A. Hinkley in 

 the vicinity of Tampico and in the State of San Luis Potosi will 

 later be submitted by him ; meantime some of the new forms are 

 described below. 



Polygyra (?) martensiana n. sp. PI. V, figs. 11, 12. 



The shell is rather thin, depressed, about the shape of P. lexasiana, 

 umbilicate, the umbilicus rapidly contracting within; surface glossy, 

 pale brownish-corneous with a faint brown band above the periphery, 

 weakly marked with unequal growth-lines. Upper surface nearly 

 flat, the spire being very low conic; periphery above the middle, the 

 base convex. "Whorls \\ to 5^, convex, slowly increasing, the first 



