ZONITES. 107 



A Post-pleiocene species, now found over the whole Interior Region. The 

 extreme points to which I have traced it are New York to Indiana, Tennessee 

 to Georgia. 



Animal resembling outwardly that of Z. ligerus. It has all Fig. 26 - 



the generic characters of Zonites. 



The specimen figured above is unusually large. There is a 



smaller, strongly earinated variety with a short, conical spire, 



Z. intertextus, var. 

 which I here figure. enlarged. 



This shell resembles some varieties of Z. ligerus so nearly, that Dr. Binney 

 hesitated some time before he considered it distinct. The spire is less high in 

 a shell of the same size, has a smaller number of whorls, and is more pyrami- 

 dal in shape than in that species. The diameter, in full-grown specimens, is 

 greater, and the base is flatter. The epidermis is darker and less shining, the 

 shell is thicker and less pellucid, the deposit of testaceous matter within the 

 aperture is less. The size of the umbilicus and the shape of the aperture are 

 the same in both. But the principal distinction consists in the spiral lines 

 which revolve on the whorl, intersecting the striae of growth, but so minute as 

 hardly to be perceptible to the naked eye, yet present in every specimen whi( h 

 I have examined. The whitish, narrow band, shaded below with rufous, ap- 

 parent on the outer, and sometimes on the second whorl, generally aids in iden- 

 tifying it, though it is sometimes wanting. Young specimens are much more 

 depressed than those of Z. ligerus, and are sometimes distinctly earinated. 

 The depression of the umbilical region is not so evident in this as in the pre- 

 ceding species. The rufous band below the white band is well defined and 

 broad, in a single specimen before me. Nearly allied as it is by its shell to 

 ligerus, it differs in a marked manner in its genitalia (see Leidy's figure in Vol. 

 I. PI. XII. Fig. 1) by having a second accessory pyriform gland to the dart sac 

 (8, 8). It may also be distinguished from ligerus by the greater number of the 

 marginal teeth on its lingual membrane. 



Z. intertextus (PI. II. Fig. L) has about 61 — 1 — 61 teeth on its lingual mem- 

 brane. There are 12 perfect laterals. Another specimen has 55 — 1 — 55, with 

 12 laterals. 



Zonites subplanus, Binney. 

 Vol. III. PI. XXXIII. 



Shell flattened, planulate above and beneath ; epidermis brownish or smoky 

 horn-color, shining ; whorls i>k, those nearest the apex striated transversely 

 with very minute and delicate wrinkles; suture distinct, not much impressed ; 

 aperture transverse, not expanded, the plane of the aperture making nearly a 

 right angle with the plane of the base of the shell ; peristome simple, thin, 

 acute; base flattened, .j^nbilieal region a little impressed; umbilicus small, 

 round, and deep, not exhibiting the volutions. Greater diameter 20, lesser 

 16 mill; height, 6 mill. 



