176 The MoUuscan Family Planorhidae 



the same form as that of Carinifex. The salivary glands extend half their 

 length behind the buccal sac and form a loop. 



The superior jaw of armigera (plate 50, fig. 2) is slightly arched, about 

 four times as wide as high and finely, vertically striated on the anterior 

 face. The side jaws are about as long as the width of the superior jaw and 

 are shaped as in Parapholyx. The jaws of jenksii (fig. 3) are the same as 

 those of armigera. 



Radula of armigera (plate 65, fig. 1). The center tooth is slightly 

 higher than wide with a bicuspid reflection which does not reach the lower 

 margin of the base of attachment. The lateral teeth (1-8) are squarish 

 with three long, spade-like cusps of the same shape. The intermediate 

 teeth (9-11) have the ectocone split two or three times, the cusps sharp. 

 The marginal teeth (12-19) are long and narrow with cusps at the lower 

 end. The endocone at first is split into two cusps about as long as the meso- 

 cone (12-13) ; they then become split into four small, equal cusps (14-16). 

 The ectoconic margin has three to four small cusps. The outer marginal 

 teeth are shorter than the earlier marginals but have the same form (19). 

 The radula of jenksii has the same form of teeth. 



Radula Data for Pkmorbula 



The data for the material examined anatomically are as follows : 

 armigera, Murphy Creek, near Madison, Wisconsin; Snodgrass Lake, On- 

 tario; Devil's Lake, Wisconsin; Douglas Lake, ]\Iich.; jenksii, Roaring 

 Brook, Unionville, Connecticut. Five specimens from each lot of armigera 

 were examined and about fifteen specimens of jenksii. 



Geographical Distribution. Planorbula is wholly an American genus 

 distributed from Great Slave Lake and Fort Smith, ^Mackenzie River, 

 south to Georgia and Louisiana, and from the New England states west to 

 Nebraska. 



Species Considered as Valid. The following are recognizable as be- 

 longing to this genus: 



Planorbula armigera armigera (Say) Planorbula jenksii (H. F. Carpenter) 



Planorbula armigera palustris Baker Planorbula campestris (Dawson) 



Planorbula crassilnbris (Walker) {^ christyi Dall) 



Geological Distribution. Pleistocene to Recent fauna. 



Remarks. Planorbula is a distinct and characteristic genus of American 

 Planorbidae. The name has been used to cover many dentate planorbids, 

 such as Tropicorbis of the tropics and certain forms of north Africa be- 

 longing to Ajroplanorbis. It is in no way related to these groups, which 

 belong in the subfamily Planorbinae. Planorbula of Haldeman belongs in 

 a separate subfamily related to Helisomatinae, having a distinct penial 

 gland and multiform prostate and ovotestis diverticula. 



The lamellae within the aperture are also different in the two groups — 

 in Tropicorbis the large lower palatal lamella is always pointed downward 



