MACROCYCLIS. 91 



The species is very nearly allied to M. concava. The differences observable 

 are the following : The size of this shell greatly exceeds the latter in all its 

 proportions, its transverse diameter being nearly twice as great. This differ- 

 ence is not caused by an increased number of whorls, for the number in both 

 is precisely the same ; but this shell seems to be projected originally upon a 

 larger scale, the nucleus being as much larger as mature specimens. The 

 color is much more yellow. The umbilicus is not so widely expanded, and 

 does not admit of counting all the whorls ; and the whorls seem to be more 

 voluminous. The striae of growth are usually coarser, and the microscopic 

 revolving striae are stronger and much more constantly present. 



It also strongly resembles M. sportella, but in that species the revolving lines 

 usually cut merely the summits of the radiating striae, without being con- 

 tinuous over the whole surface. 



Jaw crescentic, ends sharply pointed ; anterior surface ridged ; concave 

 margin smooth, with a median projection. (See p. 88, Fig. 11.) 



Lingual membrane (PI. I. Fig. B) : see p. 89. 



The genitalia are figured on PI. XII. Fig. L. The epididymis is extremely 

 long and very large, forming the peculiar feature of the system. The genital 

 bladder is oval, with a long duct, which is very much broader at the end 

 nearer the vagina. The penis sac is long, gradually tapering at its apex, 

 where it receives the vas deferens. Upon the side of the vagina, about the 

 middle of its length, is a wart-like protuberance, which may be a dart sac or a 

 vaginal prostate (d s). 



A comparison of Dr. Leidy's figure of the genitalia of M. concava in Vol. 

 I., shows considerable difference between the two species, especially in the 

 epididymis. 



Macrocyclis sportella, GOULD. 

 Vol. III. PI. XXII. a, Fig. 1. 



Shell much depressed, convex above, concave beneath, sloping into a broad, 

 tunnel-shaped umbilicus ; surface delicate and shining, of a pale, yellowish- 

 green color, regularly sculptured with sharp, coarse striae of growth, which are 

 crossed by fine, crowded, revolving lines, which usually cut merely the sum- 

 mits of the radiating ridges, so that, to the naked eye, the surface appears but 

 minutely granulated, but under a magnifier the raised spaces are seen to be 

 well-defined squares ; whorls 5, separated by a deep suture, the outer one 

 proportionally large : aperture nearly circular, a little angular at base, modified 

 by the preceding whorl ; peristome acute, simple. Greater diameter, 1 2 mill. ; 

 height, 6 mill. 



Helix sportella, GOULD, Proc. Bost. Soc. Nat. Hist., II. 167 (1846) ; Moll. Ex. 

 Ex., 37, Fig. 42 (1852) ; T. M., II. 211, PI. XXII. a, Fig. 1. W. G. BINNEY, 

 Terr. Moll., IV. 19. PFKIFFEK, Mon. Hel. Viv., I. 111. V. 246 (1868). - 

 BLAND, Ann. N. Y. Lye., VII. 366; VIII. 165. 



