occurring in Southern India. 245 



* Annals ' for April 1860) proposed the name of Plectopylis. On 

 the parietal side there is a single transverse ridge-shaped lamella, 

 with a short plait, at right angles, running forward towards the 

 aperture at the outer end, and another running backwards at 

 the extremity* nearest the inside of the whorls. The palatal 

 portion of the barrier is double, with four short raised plaits in 

 front, and two in the rear of the parietal lamina. Those in front 

 are oblique — the innermost, which is close to the parietal margin, 

 being the largest, and the outermost very small ; those behind 

 are transverse, and lie end to end. In the full-grown shell the 

 whole barrier is placed opposite to the mouth, at the distance of 

 half the cii'curaference of the whorls. 



It will be seen that, although somewhat simpler and rather 

 less numerous, the lamellae correspond generally in their arrange- 

 ment with those found in H. plectostoma, — thus forming an in- 

 teresting link between the shells of the Himalayas and those of 

 the mountains of Southern India, in addition to those already 

 noticed by my brother and myself when describing the new 

 forms of Alycaus and Diplommatina from the Nilgiris f- It is 

 singular that these genera have not yet been found in Ceylon, 

 where H. clatliratula, Pfr., is said by Mr. Benson to show a 

 resemblance to Plectopylis in the presence of internal teeth on 

 the whorl. It may be interesting to mention that new species 

 of both Alycaus and Diplommatina have lately been discovered 

 in the Kolamullies, another group of hills 100 miles east of the 

 Nilgiris, by Mr. King, of the Geological Survey of India. H. 

 retifera has also been obtained from the same hills, and from 

 the Shevaroys a third group. 



Mr. Benson, in his paper in the 'Annals^ for April 1860, 

 speaks of several epiphragms in each shell of Plectopylis, " intus 



pylis sive epiphragmatibus pluribus distantibus plicatis ob- 



structa." From the examination of a considerable number of 

 specimens of H. plectostoma, B., and H. Achatina, Gould, I am 

 persuaded that in fully adult shells there is never more than 

 one; but on examining a considerable number of partly-grown 

 specimens of H. retifera, of all ages, the existence of a greater 

 number was explained. The plaits are evidently formed close 

 behind the mouth, and exist even in a very young stage ; but 

 when the shell has been increased by nearly half a revolution J, 



* The terms "horizontal," "vertical," &c., used by Mr. Benson in re- 

 ference to the discoid Burmese and Himalayan species of Plectopylis, 

 would cause confusion if applied to the trochiform H. retifera. Trans- 

 verse and longitudinal are simply used above in reference to the whorls of 

 the shell. 



f Journal of the Asiatic Society of Bengal, 1860, vol. xxix. p. 11.9. 



X In some of the species the distance is probably greater between the 

 series of teeth. In H. Achatina it is nearly a whole revolution. 



