76 LAND AND FRESHWATER 



may be useful here, to show how very near it is to the Singapur 

 shell in all its characters, and as a proof of the range eastward of 

 the genixs Hemiplecta : — " Animal. The extremity of the foot is 

 rather square, the mucous gland large, not extending to the sole of 

 the foot, and with apparently no overhanging lobe. The right 

 dorsal lobe is of usual size, but the left is very poorly developed, 

 being very narrow and separated into two parts, the posterior 

 portion being narrow and only 6 millim. long; in the space between 

 them lies a small left shell-lobe, flat and tongue-shaped ; a right 

 shell-lobe is also present, which would appear in life to be broad 

 and triangular in outline. 



"The odontophore [figs. 2-2 i] is like that of H. JitimpJirei/siana 

 from Hiugapur, the type of the ^enxxs hemiplecta. Jaw circular, no 

 central projection [fig. 2 c]. 



" The shells had been taken evidently in the cold season, and the 

 generative organs were not fully developed in the specimens I 

 dissected, but enough was seen to show the presence of a long 

 simple amatorial organ, and the male organ also, as in Ileviiphcta." 



Semper has placed five South-Indian shells* (included in the 

 above list of IIemij)h'cfa of different authors) in the genus Xesta. 

 Heyn'qilecta, as I said before, he does not recognize ; and he splits 

 Xesta up into 3 sections, not indicated by subgeneric titles. These 

 sections have, I think, too many differences iiiter se to be retained in 

 the same genus. His first group is entirely confined to the South 

 Indian Peninsular area, possesses no shell-lobes, and has tricuspid 

 central teeth and bicuspid or aculeate laterals, few in number in the 

 row. The second group is represented by one species — cuminyi, of 

 Mindanao — very distinct, with large expanded mantle-lobes, as in 

 / , the Helicarion division. The third is the Malayan group, with 



tongue-shaped shell-lobes and neck-lobe (dorsal lobe) in two lappets, 

 containing the very distinct and a typical species of Albers's genus 

 Xesta, viz. citrina, together with distincta and mindanensis. The 

 first group must be now considered quite distinct, as I shall show 

 and refer to it further on ; the second must be placed elsewhere ; 

 and the third remains as Semper put it, and forms a very charac- 

 teristic genus of the islands of the Malay Archipelago. It is 

 fortunate that Albcrs, in his original description of Xesta (' Die 

 Heliceen,' 1850, p. 58), places citrina at the head of the list of 

 species ; otherwise there might have been a doubt as to whether 

 citrina or stuartioi was the typical shell. There are certain re- 

 semblances, as might be expected, between Uemijdecta 7mm- 

 jjhrei/siana and Xesta citrina and X. distincta which bring these two 

 subgenera near each other, particularly in the odontophore ; both 

 have 350 and 300 teeth respectively in the row, and of the same 

 simple straight form as regards the central teeth ; but the very long 

 thread-like bursa seminalis with globular end in X. citrina is a 

 marked difference in the generative organs. 



* Ligulata, tranquebarica, madcraspatana, helangeri, bistrialis. 



