ON SOME LAND AND AQUATIC SHELLS FROM 



MARIA ISLAND. 



By W. F. Petterd. 



I herewith submit a list of the species of land and fresh 

 water testacea which were recently collected on Maria Island, 

 East Coast. It includes several which have but a restricted 

 distribution on the adjacent mainland, and the somewhat re- 

 markable association of species is of more than passing- 

 interest, although the majority are such as are to be found 

 widely dispersed. The appearance at this insular locality of 

 the local Helix sinclairi is quite unexpected, and H. lottah 

 and H. nelsonensis have strayed far away from their origin- 

 ally recorded habitats. 



The almost microscopic H. halli is not usually an abundant 

 species, but here it appears in considerable quantity, and is 

 in fact the most common of the smaller forms. There are 

 also several specimens of a new species with little affinity to 

 any already known. Of the two species of aquatic shells, 

 one is quite a new departure in the Ancylus, not only as 

 regards our local molluscan fauna, but as well as relates to 

 the genus generally. 



Its unique characteristic is the widely-spreading margin of 

 the aperture, a peculiarity not to be found in any of the 

 numerous species of the genus. This remarkable departure 

 from the normal condition, in a genus which affords but 

 limited variation in general structural j^eculiarities, is difficult 

 to adequately account for, but it would appear to afford a 

 stronger attachment, and may thus resist disturbance in a 

 swiftly flowing stream. 



Description of New Species. 



1. Ancylus marise, n. sp. 



Shell small, thin horn-brown colour, broadly irregularly 

 ovate, concentrically striate, with well marked lines of growth. 

 Aperture extremely large, the margins broadly, prominently, 

 and flatly expanded, thus forming an irregular base of 

 attachment. Apex prominent, ol>tuse, oblique, and sub- 

 marginal. 



Long., 5 ; lat., 3i ; alt., 2| mill. 



Habitat : Maria Island, East Coast, attached to submerged 

 stones and aquatic plants in a small running stream. 



This is a very peculiar form of a genus which has several 

 representatives on the mainland. In its young state it has 

 much the general appearance of A, tasmanicus, Tenison 



