PACIFIC COAST SPECIES. 83 



servable are the followiug: The size of this shell greatly exceeds the 

 latter in all its proportions, its transverse diameter being nearly twice 

 as great. This difference 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 count- 

 ing all the whorls; and the whorls seem to be more voluminous. The 

 stri» of growth are usually coarser, and the microscopic revolving striae 

 are stronger and much more constantly present. 



A dark reddish variety was found by Mr. Dall in Alaska. 



It also strongly resembles M. sportella^ but in that species the revolv- 

 ing lines usually cut merely the summits of the radiating striae, without 

 being continuous over the whole surface. 



Jaw crescentic, ends sharply pointed; anterior surface ridged; con- 

 cave margin smooth, with a median projection. (See p. 79, Fig. 42.) 



Lingual membrane (see'p. 80) ; the figure here given shows the char- 

 acters of the individual teeth. 



The genitalia are figured on Plate XII, Fig. L, of Terr. Moll., V. 

 The epididymis is extremely long and very large, form- fig. 45. 



ing 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 Linfruai dentition of 



M. Yancouverensis. 



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 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. 



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

 a broad, tuunel-shaped umbilicus; surface delicate and .shin- fig. 46. 

 ing, of a pale, yellowish-green color, regularly sculptured 

 with sharj), coarse strise of growth, which are crossed by 



Jlacrocycliis 



fine, crowded, revolving lines, which usually cut merely the Kporteiia. 

 summits 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 cir- 



