108 Records of tlie Indian Museuvi. [Vol. Xl\ , 



the same size as the type of L. howelli. The following are the measure- 

 ments of a specimen : — 



mm. 



Length ... ... ... ... . ... ... 9 



Greatest breadth ... ... ... ... ... 6-5 



Length of aperture ... ... ... ... ... 6-25 



Greatest breadth of aperture ... ... ... ... 3-75 



The shell occurs abundantly in the friable clay of the He-Ho lake- 

 deposit at an altitude of about 3,600 feet. The specimens are well 

 preserved so far as form is concerned, but difficult to extract in a per- 

 fect condition owing to their fragility. They have evidently sunk to 

 the bottom of an open lake and there been buried in very fine mud. 

 This phase is, therefore, the most ancient with which we are acquainted 

 as well as the nearest to the Tibetan species. It is very constant. 



Phase B. 



The shell is still narrower than in phase A and the aperture, which 

 is of about the same length, is constricted posteriorly. The suture is 

 still more oblique and the apical whorl is reduced in size. The shell 

 is rather thick and has still coarser growth-lines. There is no great 

 divergence in size from the former phase. The measurements of 

 shells are as follows : — 



mm. mm. mm. 



Length ... ... ... ... 10 9 8-5 



Greatest breadth ... ... ... 6 5-75 5 



Length of aperture ... ... ... 6-5 6 5-75 



Greatest breadth of aperture ... ... 3-75 3-5 3 



Shells are abundant in the superficial deposit on the banks of the 

 He-Ho river just before it plunges down towards the Inle plain, about 

 a mile to a mile and a half east of the point where the types of phase 

 A were discovered and at a slightly lower altitude. It is probable that 

 the deposits represent the debris at the edge of a marsh or lake. The 

 shells are sometimes slightly waterworn and as a rule more or less broken. 

 I class them as subfossil. They also are constant. 



Phase C. 



This is the only phase I have seen in a living condition. The shell 

 is thin and fragile but of a rather dark brown colour. It is a little 

 narrower and more acuminate than that of phase B and has the apical 

 whorl still smaller, but the suture is not quite so sinuous and the aper- 

 ture is not so contracted posteriorly. The growth-lines are conspicu- 

 ous but not so coarse. The rimation, though quite distinct, is less 

 strong. The shell is rather larger ; the following are measurements of 

 two specimens : — 



mm. mm. 

 Length ... ... ... ... ... 10-25 8 



Greatest breadth ... ... ... ... 6 4-25 



Length of aperture ... ... ... ... 7 5 



Greatest breadth of aperture ... ... ... 4 2-25 



