SubjaniiUes, Genera, and Subgenera — Recent and Fossil 99 



nidamcntal gland and about 1.5 mm. long. The albumen gland is rather 

 small and oval in shape. 



Hermaphrodite Organs. The ovotestis (plate 3, fig. 2) consists of rela- 

 tively few (less than twenty) large club-shaped diverticula. They are 

 placed in a double row on the ovisperm duct. The ovisperm duct between 

 seminal vesicle and ovotestis is very short, but anteriorly, betw^een the 

 seminal vesicle and the oviduct, it is a long (2 mm.), narrow tube. 



The figures on plates 2 and 3 agree in the main with those already 

 published by European malacologists. L. Soos's figure (1917, p. 44, fig. 17) 

 is the same, showing the few large ovotestis diverticula, the elongated 

 spermatheca and duct, and the few diverticula on the prostate. The flagella 

 are shown somewhat longer than those in the figure on plate 3. Germain's 

 figure (1931, p. 543, fig. 56) is practically the same, the flagella being 

 more like the figure on plate 3. 



Respiratory and Renal Systems, The pseudobranch (plate 3, fig. 4) is 

 rather small, smooth, elongate-ovate, and folded. The pneumostome is 

 very large (fig. 4, PS). 



The kidney (plate 47, fig. 22) is very long (8 mm.) and narrow, ribbon- 

 like, the short ureter reflected at right angles to the kidney. In cross sec- 

 tion (fig. 23, below the middle) it is seen to be rounded, a trifle wider than 

 high, with the veins placed at the upper corners of the lumen, which is 

 oval in sha]K'. There is no superposed ridge. 



Digestive System. The stomach region (plate 48, fig. 16) is very nar- 

 row, divided into crop, gizzard, and pyloris. There is a short blind sac. 

 The intestine makes a sharp turn about the stomach and another around 

 the liver, then runs forward to the rectum. 



The buccal sac is much elongated, the salivary glands short, wide, and 

 looped behind. There is a conspicuous radula sac which projects notably 

 from the rear end of the buccal sac. 



The jaw (plate 50, fig. 24) is horseshoe-shaped, and composed of many 

 small plates (about sixtv). It is similar in form to that of Planorbis. 



Radula (plate 69, fig. 7). The formula is 23-1-23 with 164 rows of 

 teeth. The central tooth is wdder at the lower edge of the base of attach- 

 ment than at the upper margin of the tooth. The two short cusps do not 

 reach the lower margin of the base of attachment. Lateral teeth (1-7) 

 long and narrow, the reflection low and wide and placed high up on the 

 tooth. There are seven cusps, dagger-like and subecjual in size, the ecto- 

 conic cusps a trifle smaller. There are six teeth which may be called inter- 

 mediate (8-13), since the cusps are a trifle smaller than those of the lateral 

 teeth. ^larginal teeth (14-21) with the reflection very low and wide, 7- 

 cuspid, the mesocone a trifle larger than the three cusps on each side. The 

 outer marginals (22, 23) are vestigial. The teeth are all crow^led on the 

 membrane, some of them even overlapping. The teeth are very uniform in 

 size and shape. 



Twelve specimens of Segmentina nitida were dissected, collected from 

 marshes in a meadow in Czerniakow, a suburb of Warsaw, Poland, by 

 A. Jankowski. 



Geographical Distribution. Typical Segmentina is distributed through- 

 out Europe and northern Asia. A single species, 5. nitida (Miiller), is recog- 

 nized, with several races, by Westerlund and others. Some small species, as 



