igiS.] H. H. Godwin-Austen : Mollusca, VIII. 583 



and triangular, just overlapping the peristome ; the left dorsal 

 lobes are quite separate one from the other. 



The generative organs are comparable to those of M. hard- 

 wickei of Calcutta ; the penis with the short retractor muscle, 

 the coiled caecum and the kale-sac or flagellum are all exactly 

 similar 



The radula is like that of the Calcutta species, 40.2. 13. 1. 13. 

 2.40 or 55.1.55. 



The general similarity of structure in the animals of the 

 Calcutta species of M. hardwickei and its variety politulus of 

 Eastern Assam is notable ; it is an extended range of some 750 

 miles from the delta of the Ganges in one direction keeping to the 

 valley of the Brahmaputra, and up into the gorge of the Tsanspu 

 one feeder, up the Lohit to Brahmakund another. 



It may be also noted that neither M. hardwickei nor its 

 variety have as yet been recorded from the Teesta Valley, nor 

 from the Gangetic side, nor from Sylhet and Cachar that is on the 

 Surma tributary of the Brahmaputra. There we can follow an- 

 other species common in Calcutta, M . indica. 



We may take it for granted that the course of distribution has 

 been from the north eastward, with the flow of the rivers to the 

 delta; that long after M. h. politulus was developed the waves 

 of the Indian Ocean were beating on the beach line where Calcutta 

 now stands, and may be even far further up the delta. This 

 carries us a step further back to the development of M. hard- 

 wickei in the North-Bastern Himalayan Range, where so many 

 great rivers marking ancient valleys all unite to form the Brahma- 

 putra, and from whence it spread along the base of the mountains, 

 on the north to the Miri and Dafla and Bhutan, on the south to the 

 Singpho and Naga. 



Macrochlamys bapuensis, n. sp. 

 (Plate li, figs, i, la.) 



Locality. — Abor Hills, near Bapu, H.S. {Capt. G. F. T. Oakes). 

 Shimang, Abor Hills, young shells {Capt. G. F. T. Oakes). Abor 

 Hills, in spirit {Capt. G. F. T. Oakes). 



Shell depressedly conoid, rather flat below, perforate, a 

 strong epidermis; sculpture coarse regular well-defined striation, 

 in the Shimang specimen sculpture rather strong and very regular 

 striation, in the Abor Hills specimen in spirit sculpture coarse 

 wavy regular parallel striation ; colour umber brown ; spire de- 

 pressed, apex flatly rounded ; suture shallow; vi/horls5, well round- 

 ed on the periphery, flattened above ; aperture widely lunate, sub- 

 vertical ; peristome thin ; columellar margin short, reflection near 

 umbilicus, very oblique. 



Size: major diameter 23*0, minor 20'o, alt. axis 8*o mm. 

 The young shells from Shimang have the following dimensions : 

 maj. diam. 17*0, minor 14*0, alt. axis 6'0 mm. 



