Subfamilies, Genera, and Subgenera — Recent and Fossil 127 



but is otherwise similar to typical anceps. The form of the section may 

 vary when taken from different parts of the kidney, as is shown in several 

 sj^ecies of Helisoina. 



Digestive System. The stomach is bulbous and tapers into the pyloris. 

 The intestine loops around the stomach, passes over the oesophagus, turns 

 backward in a long loop around the liver and then runs forward to the 

 l^seudobranch in the form of the rectum. The general form is like that of 

 HeUsomn trivolvis shown in fig. 1 on plate 48. 



The buccal sac is short-ovate. The salivary glands are narrow and 

 about twice as long as the buccal sac. They are joined behind. 



The jaw (plate 49, fig. 1). There is one wide, low, arched superior jaw 

 (about 1 mm. wide) and two narrow, ribbon-like lateral jaws somewhat 

 longer than the superior jaw. The superior jaw is finely striated on its 

 anterior face. 



The radula has the variable formula 22-1-22 to 30-1-30, with 150 to 193 

 rows of teeth. A radula from specimens from Maple River, Michigan, is 

 figured on plate 53, fig. 1. The center tooth is squarish with two short, 

 wide cusps. The lateral teeth (1-5) have a squarish reflection which ex- 

 tends well below the lower margin of the base of attachment. The cusps 

 are spade-shaped, the mesocone the longest and the ectocone the shortest. 

 The ectocone of the fourth tooth is split into four small cusps. The inter- 

 mediate teeth (6-7) are narrower than the lateral teeth, the base of at- 

 tachment very short. The entocone is broken up into two or three small 

 cusps and several small cusps appear on the outer edge of the tooth above 

 the ectocone. The marginal teeth (8-14) are much narrower, this feature 

 increasing toward the outer margin of the membrane where the teeth are 

 ^'ery long and narrow (14). In the marginal teeth the entocone is broken 

 up into fine serrations numbering from five to ten cusps, the number in- 

 creasing in the outer teeth (compare 8 and 14). The mesocone becomes 

 somewhat smaller but is not modified. The ectocone is distinct in the 8th 

 tooth with three small cusps above it. From the 10th tooth this area 

 changes to small serrations five to six in number. The outer marginal teeth 

 appear like a saw, wdth one large tooth (the mesocone) in the center 

 (see 14). The extreme outer marginals are vestigial. 



The radulae of anceps and its races vary considerably, principally in 

 the numerical formulae, but also in the number and position of the cusps. 

 The table below indicates the extent of this variation. The columns are 

 all as follows, reading from left to right: Locality, formula, lateral teeth, 

 intermediate teeth, plate, and figure. 

 Helisoma anceps (Menke). 



Maple River, Michigan 23-1-23 to 24-1-24 1-5 6-7 Plate 53, fig. 1 



I'nionville, Conneotiout 23-1-23 to 25-1-25 1-5 6-7 Plate 53, fig. 3 



ChautaiKiua Lake, New York 22-1-22 to 25-1-25 1-7 8-9 Plate 53, fig. 2 



Moo^ie Ear Creek, Wisconsin 26-1-26 to 27-1-27 1-6 7-9 



Cleveland, Oneida L., New York 25-1-25 to 27-1-27 1-6 7-S 



There are 150 to 160 rows of teeth. 

 HcUsoinn anceps sayi F. C. Baker. 



Bayfield, Wisconsin 27-1-27 to 27-1-27 1-5 6-7 Plate 53, fig. 4 



Helisonta anceps percarinatuni (Walker). 



Douglas Lake, Michigan 27-1-27 to 30-1-30 1-8 9-10 Plate 54, fig. 1 



There are 193 rows of teeth. 



