198 INVERTEBRATA OF MASSACHUSETTS. 



or six, the lower one three fourths of the length of the shell, the 

 others, separated by a distinct suture, and flattened, form a short, 

 blunt spire ; aperture long and narrow, broadest below ; outer lip 

 thin and sharp, the posterior third suddenly bending inwards joins 

 the body of the shell by a very acute angle ; the inner lip, usually 

 covered with enamel, has two folds upon it, a transverse one be- 

 low the middle, and another formed by the outer lip as it rises and 

 turns within the shell ; this portion is usually white ; within the 

 outer lip are occasionally to be found from one to four elevated, 

 white, revolving ridges, not reaching the edge of the lip. Length 

 inch, breadth T 3 ff inch, divergence 68. 



Inhabits marshes that are occasionally overflowed by the tide, 

 and never far below high-water mark. They frequently crawl up 

 the stems of grasses at the margins of inlets, apparently to escape 

 the rising tide. In October, 1839, I observed great numbers of 

 them at Oak Island, a small, wooded upland spot in Chelsea, sur- 

 rounded by salt marsh. They were burying themselves under 

 the leaves, and in the loose earth at the base of rotten stumps. 

 This spot is now never overflowed by the tide. I have also two 

 specimens brought from Windsor, Vermont, which I was assured 

 were obtained there, living with Planorbis armigerus. 



The animal is reddish-brown above, paler beneath, foot about 

 the -length and breadth of the shell, broad before, and bluntly 

 pointed behind, the margins somewhat scolloped, or undulated, 

 and divided across at about the anterior third ; tentacula slender 

 and tapering, the eyes at the inside of the base ; rostrum nearly as 

 long as the tentacula, with an expanded lobe each side. 



This shell, with its kindred species, is very peculiar in its structure 

 and habits. It belongs to the genus MELA'MPUS of Montfort, CONO'V- 

 ULUS of Lamarck ; but it seems to be the received opinion that there 

 are no characters to authorize a separation from AURI'CTTLA. 



The perfect shells are smooth and brown, with usually three or four 

 darker, narrow bands ; but the shells soon become eroded, and the 

 surface is left rough, and of a greyish color. The ridges within the 

 outer lip are not seen except in aged shells. 



There is an English shell named Valuta Hdentata, which, if it is 

 not a variety of V. denticulata, would form a species under this genus. 

 In that case we must adopt the specific name A. cornea for our shell, 

 given by Deshayes. 



