Subfmnilies, Genera, and Subgenera — Recent and Fossil 103 



is a larj^e blind sac. The buccal sac is elongated, narrowed in front with a 

 large radiila sac behind. The salivary glands are short and do not extend 

 far beyond the posterior end of the buccal sac. They are joined behind as 

 in Scgmcntina. 



The jaw is fragmented as in Segmentina and is made up of many 

 small plates. 



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

 is higher than wide with two wide cusjis which do not reach the lower 

 margin of the base of attachment. The laterals (1-9) are squarish and 

 tricuspid, the mesocone large and almost reaching the lower margin of 

 the base of attachment. The entocone is shorter than the mesocone. The 

 cctocone is shorter than the entocone and is placed high on the margin of 

 the tooth. In the marginal teeth the reflection is wide and low and is placed 

 high u\) on the tooth. The entocone and mesocone are of equal length and 

 the ectocone is shorter with two small cusps above on "the outer margin of 

 the tooth. The radula teeth of Hippeutis resemble those of Bathyomphahis 

 contortus shown on plate 68, fig. 1. They are not like those of Scgmcntina 

 nitida figured on plate 69, fig. 7. 



The above anatomical information was obtained from specimens col- 

 lected in a pool on a meadow in Jabtonna, 16 km. north of Warsaw, 

 Poland. The specimens were obtained by Mr. A. Jankowski. 



Geographical Distribution. Europe from Great Britain, Norway, and 

 Sweden south to Portugal. Italy, and Albania. Eastward to northern 

 Siberia. A palearctic group. It has been recorded from northern Africa and 

 the group may be circum-]\Iediterranean in distribution. As in Segmentina 

 a number of species have been described with many varieties. The species 

 cited from South x\frica, India, and China probably belong in other genera. 



Species Considered as Valid. The following species are apparently 

 referable to Hippeutis: 



Hippeutis complanatus (Linn.) Hippeutis raymondi (Bgt.) 



Hippeutis riparius (Westerlund) Hippeutis junodi (Connolly) 



Hippeutis syraciisanus (Cafici) Hippeutis benguelensis (Dunker) 



Hippeutis diaphaneUus (Bgt.) 



Geological Distribution. From the Lower Eocene period (Wenz). 

 Eighteen species and races of fossil Planorbis are referred to this genus 

 by Wenz. 



Remarks. Hippeutis complanatus resembles Segmentina nitida in its 

 anatomy. The prostate, however, has fewer diverticula. The penial gland 

 differs in shape but both are attached to the right pilaster. The whole 

 genitalia of Segmentina are much elongated while these organs in Hippeutis 

 are short and heavy. Internally the penial complex of the two groups 

 differs in details. The kidneys of the two genera are quite unlike. The 

 radula resembles Bathyomphahis rather than Segmentina. The shell is 

 wholly without barriers or lamellae of any kind within the aperture and 

 this characteristic at once marks Hippeutis as a separate genus. 



Species from northern Africa and eastern Asia have been assigned to 

 Hippeutis but until these species have been examined anatomically this 

 reference remains open to doubt. The Asiatic forms probably belong to 

 Benson's genus Helicorbis. Parasites were not observed in any of the 

 material examined. 



