Subfamilies, Genera, and Subgenera — Recent and Fossil 77 



divertieuhi which upi)ear widely fjpaeecl while there were thirteen crowded 

 diverticula in the specimens personally examined. The separate prostate 

 duct is not shown in Soos's figure. The spermatheca in Soos's figure is also 

 on a longer duct. The penial complex differs in several respects. 



In 1929 (p)). 22, 30) Odhner called attention to the absence of a stylet 

 in Armigcr, figured the verge of Anniger crista to show the absence of the 

 stylet and the i)resence of a small penial i)apilla. This is, apparently, the 

 first indication of this anatomical difference between Armiger and 

 Gyraulus. Odhner noted a difference in the size of the teeth and formula of 

 crista, those from the Takern having much smaller teeth than specimens 

 from near Stockholm. The formula, also, was only 11-1-11 while the 

 larger form has a formula of 14-1-14. 



Germain (1931, ii. 540) says 'Appareil genital comme chez les especes 

 du sous-genre Gyraidus.' But this is not the case. There is no stylet at 

 the end of the verge and the opening of the sperm canal is at the center 

 beside a small papilla and not at the side above a stylet as in Gyraulus. 

 The seminal vesicle is also different in form of glands. These differences in 

 anatomy are sufficient to remove Armiger as a subgenus of Gyraulus and 

 indicate its right to full generic rank. The genitalia of Armiger and Torquis 

 may be compared on i^late 18, where the difference in the structure of the 

 termination of the verge is i)lainly indicated. 



Respiratory and Renal Systems. The pseudobranch (plate 18, fig. 6) 

 is broadly triangular, leaf-like. The rectum is a large tube bordering the 

 upper side of the pseudobranch and the anus is above the pseudobranch. 



The kidney (plate 47, fig. 20) is short and wdde, somewhat resembling 

 the kidney of Gyraidus vermicularis (fig. 3). A section through the kidney 

 near the middle (fig. 21) shows it to be flattened, convex above, with the 

 veins near the center of each side of the oval lumen. The section is also 

 similar to that of Gyraulus vermicidaris (fig. 7). 



Digestive System. In the region of the stomach (plate 48, fig. 15) there 

 is a distinct division into crop, gizzard, and pyloris. The intestine makes a 

 loop forward and then backward under the oesophagus. It bends around 

 the liver and turns forward, ending in the rectum on the pseudobranch. 

 The stomach region resembles that of Gyraulus (fig. 13). The buccal sac is 

 like that of Gyraidus. 



The jaw (plate 50, fig. 20) is narrow and characteristically horseshoe- 

 shaped with the lateral processes elongated. There are twenty-two plates in 

 the upper or superior jaw and fourteen to sixteen plates in each of the side 

 jaws. The jaw most nearly resembles that of Gyraidus circumstriatus (fig. 

 22) except that it bears a larger number of plates. 



The radula formula is 16-1-16 with 150 rows of teeth. The center tooth 

 is bicusj^id and resembles that of Gyraulus vermicularis (fig. 5). The 

 laterals are four-cuspid (1-9), the intermediate teeth (10-11) five-cuspid, 

 and the marginals (12-13) six-cuspid. The outer marginals are vestigial. 

 The teeth resemble those of Gyraulus except that there is always an 

 accessory cusp above the ectocone, even in the lateral teeth. 



For the above anatomical data ten specimens were dissected, collected 

 from a swamp on University Bay, Lake ]\Iendota. near [Madison, Wiscon- 

 sin, by Dr. J. P. E. [Morrison. These represent the variety i}nbricatus. 

 Typical crista from a pond in Krolikarnia, a suburb of Warsaw, Poland, 

 collected by A. Jankowski. provided most of the anatomical data. 



