1871 ] F. StoHczka — Notes on terrestrial Mollusoa. 161 



few possess also small teeth on the outer and columellar lips. 

 The same group of St rep tax is, with a single parietal fold, also 

 extends to the islands of the Indian Archipelago and to China on 

 the one, Mauritius and the Seychelles on the other hand. 



The animals of Streptaxis are characterized, as already noticed, 

 by the great length of the anterior part of the body,* while the 

 posterior part, or the foot, is very short and often barely protrudes 

 beyond the apex of the shell, when the animal creeps about. The sole 

 of the foot is usually grooved along the middle, but not distinctly. 



I am not aware that the anatomy of any of the Indo-Malayan 

 species of Streptaxis has been published, and I give, therefore, a 

 short account of that of St. obtusus and Burmanicus. 



St. out as us. An inspection of fig. 1, on pi. viii, will shew that 

 in the main points the organs are quite similarly arranged as in 

 the Heliclcle, only with some modifications adapted to the shape 

 of the animal. The mantle is above, at the pulmonary orifice, con- 

 siderably produced, receding ventrally, but remaining entire. On 

 the inner side it has near the margin an elongated, thickened 

 appendage on each side of the pulmonary opening. The pulmonary 

 cavity itself is very long, but the lungs narrow, the reticulations 

 being very fine and mostly simple. The digestive system differs 

 from all Helicid^e which I have examined, by the peculiar develop- 

 ment of the buccal parts. The mouth is wide, and immediately 

 behind it, where it makes an angle, lies the nervous ring, consist- 

 ing above of two larger, and below of two smaller ganglions, the 

 latter being connected by a narrower bridge than the former. Im- 

 mediately behind the nervous ring, the buccal parts are produced 

 into a cylindrical muscular tube which extends in a slight curve 

 up to the end of the chief retractor muscle of the body, where 

 it is firmly attached by a special, thick, muscle. A few separated 

 threads connect the mouth direct with the anterior end of the 

 retractor. The ring-muscles forming the outer layer of the tube are 

 almost horny, or at least very tough. The longitudinal muscles form- 

 ing the internal layer are much softer, but considerably thicker. 



* See pi. viii, fig. 6. Streptaxis Pfeifferianus from Camorta, one of the 

 Nieobar islands. Body bright yellow, pedicles coral red, this colour tinging the 

 back. Lives under dead leaves in forests. 



