Mr. W. H. Benson on the Genus Camptoceras. ll 



of Camptoceras, sinks into a widely-spread, depressed cone, with 

 scarcely any distortion of the spire. 



The animal adheres, in deep water, to the decaying stems of 

 a reedy sedge, more frequently burrowing into them, and con- 

 cealing itself between the internal layers ; a habit which renders 

 it difficult to detect. 



When my lamented friend Dr. Bacon found the first specimens 

 in my presence, the idea which immediately presented itself was 

 that the shell was a monstrosity; however, an examination of 

 the animal, its peculiar habits, the absence of any known shell, 

 in the whole of India, of which it could possibly be a distorted 

 variety, and the persistence of character in some sixty specimens, 

 secured at various times, all concurred to dispel such a sup- 

 position. 



The shell was very local, occurring in one piece of water only, 

 of several which had evidently once formed a portion of the bed 

 of the Ram Gunga River. Singularly enough, Flanorbis Calathus, 

 which we had only met with in the mountains, distant 100 miles, 

 and at an altitude of 4000 feet, was likewise detected in, and 

 found to be nearly restricted to, this water. In a neighbouring 

 pond, similarly circumstanced, Planorbis coenosus, nobis, was 

 exclusively obtained ; and to a third lagoon, in the immediate 

 vicinity, was confined the shallow Ancylus Verruca, nobis, which 

 I had discovered in the mountains accompanying Planorbis 

 Calathus, but which proved to be also abundant in the weedy 

 channel of the Rajhera, distant a few miles from Moradabad. It 

 appeared as if the original habitat of Camptoceras had been the 

 scarcely explored woody mountains which give birth to the 

 Ram Gunga, and that in a former course of the river through the 

 broad alluvial bed in which it now wanders, these unwonted 

 forms had been capriciously distributed in the deep hollows 

 which had become disconnected by the retirement of the stream. 



The short periodic appearance, on high grounds, near the 

 ponds in question, of the rare Planorbis Rotula, nobis. Annals, 

 vol. V. 1850, page 351 (since figured by Dunker), illustrates the 

 uncertain appearance of some species of freshwater shells; and 

 of this Camptoceras also affords an example. After the first cap- 

 tures, towards the end of February 1842, specimens were with 

 difficulty procurable. In March 1843 I could not find more 

 than three individuals, and Dr. Bacon was altogether unsuc- 

 cessful. A like want of success attended a cursory effort which 

 we made at the end of 1 845. It would appear as if our researches 

 had exhausted the supplies of the shell, which had taken pos- 

 session of the water plants, within reach from the banks of the 

 lagoon, and no means were at hand for exploring those which 

 were farther from the shore. Possibly the animal may have 



