200 The Molluscan Family Plauorbidae 



is a large, thin lobe and is capable of considerable extension (fig. 4, PS). 

 In fig. 2, it is shown turned back and sjiread open. 



The pseudobranch is highly vascular, well-supplied with blood vessels, 

 veins, and muscles. It more nearly resembles the molluscan branchiuni 

 than the pseudobranch of any of the other fresh-water pulmonates. 



The kidney is long and narrow (12 mm. long, 1.5 to 3 mm. wide). The 

 ureter is 1.5 mm. long and is sharply reflexed against the lower part of the 

 kidney, pointing backward and upward into the mantle cavity. In form, 

 the kidney resembles that of Helisoma trivolvis figured on plate 44 (fig. 2). 

 The reflexed ureter in the s})ecimens examined is not so long as figured by 

 Rao ( 1923, p. 206) . A cross section near the middle (plate 45, fig. 19) shows 

 a high, thick, wide ridge. The lumen is rounded and shows internal folds 

 or septa. A large vein lies on each side of the lumen. The cross section 

 somewhat resembles that of the kidney of Planorbarius corneus (plate 45, 

 fig. 18). The kidney of Indoplanorbis is noteworthy for the size and width 

 of the superposed ridge, which resembles some of the large Hclisotna 

 species (as Helisoma pilsbryi, plate 44, fig. 12). 



Digestive System. The stomach resembles that organ in Australorbis 

 glabratiis (i)late 48, figs. 9, 10). The intestine first makes a loop around the 

 stomach, passes backward to the posterior part of the liver, then makes 

 another loop and passes forward to the enlarged rectum, which has its 

 exit in the anus above the pseudobranch. There is a narrow, low ridge on 

 the rectum which ends near the pseudobranch. There is a large caecum or 

 blind sac near the pyloric portion of the stomach. 



The buccal sac is short, wide, and high. Viewed from above, it is 

 roughly heart-shaped. The radula sac is represented by a wide, flatly 

 rounded bulge at the lower posterior extremity of the buccal sac. The two 

 salivary glands are rather long, about one and a half times as long as 

 the buccal sac when fully extended. In the natural position, the posterior 

 ]iortion of tiie salivary glands (somewhat less than half the length) is 

 floubled backward beneath the anterior portion, which is wider with larger 

 glandular lobules. The ducts are short and narrow. The salivary glands 

 are joined behind as in Helisoma and other planorbids. 



The jaws (plate 50, fig. 10) consist of a wide and low superior jaw, 

 striated on its outer face, slightly bent downward at the ends. The lateral 

 jaws are in the form of a question mark, are very narrow and about as 

 long as the width of the superior jaw. The jaws of Indoplanorbis do not 

 differ notably from the jaws of the subfamily Helisomatinae. 



The center tooth of the radula (plate 66, fig. 1) is higher than wide, 

 rather narrow, the reflection broadly bicuspid and reaching nearly to the 

 lower margin of the base of attachment. Lateral teeth (1-5), squarish, 

 tricuspid, the mesocone the longest, the ectocone the shortest and i)laced 

 high up on the reflection, all cusps wide and spade-shaped. Intermediate 

 teeth (6-11) narrower, differing from the typical laterals in having a sec- 

 ond small cus]) above the ectocone. The tenth intermediate tooth has two 

 small cusps above the ectocone. Marginal teeth ( 12-26) narrow, about 

 three times as long as broad. The entocone is split into three to five small, 

 subequal cusps, the mesocone is larger and distinct, and the ectocone is 

 smaller with two to three small cusps above it on the outer margin of the 

 tooth. The outer marginal teeth (27, 32) are still narrower and the lower 

 edge of the reflection is minutely denticulated. The extreme outer marginal 

 teeth are very small (33) . 



