122 



Proceedings of the Royal Irish Academy. 



species; and outside tlie centraLlimestuue 

 districts, it is only found in isolated 

 stations in West Galwoy, "\Yest Mayo, 

 Sligo, and Leitrim ; all these stations, 

 however, lie on CarLoiiiferous lime- 

 stone. So far this shell has not been 

 found in any division in Ulster, and its 

 absence from the rermanagh lakes, 

 ■where so many " Central " species, such 

 as Planoibis vortex auA Anodonta cygnea, 

 occur, is worthy of special notice. Its 

 chief habitats are canals and the larger 

 rivers and lakes, the Shannon being 

 perhaps its present headquarters. In 

 colour and markings there is considerable 

 varlatiou. 



LAMELLIBEA]N^CHIATA. 



UNIONIDAE. 



Margaritana margaritifera Liune. 



Mya margaritifera, Brown, Mom. AVeruer. 

 Soc, vol. ii, p. 505, 1818. Alasmodon 

 margaritiferus and A. elongatus, 

 Thompson, Cat. L. and F. W. MoU. 

 of Ireland, pp. 41 and 44, 1840. 

 Unio margaritifer, Scharif, Irish Nat. 

 p. 180, 1892. 



WD ED LD AN 

 FE TY AR DO 

 WMSL LE MO 

 EM EO CY LH 



WC NG LF WH ME 

 SG KG KI) DU 



CL NT QC CW Wl 

 NK LK ST KK WX 

 SK MC EC WA 



WC 



Abundant in manT of the larger 



rivers in the mountainous parts of 

 the south, west, and north, and also 

 frequent in some of those in the east. 

 As might be expected, it is absent fi'om 

 most of the central jDarts of the country, 

 ■where it is replaced in many of the 

 rivers by Anodonta cygnea. Specimens 

 from the Aughrim lliver in Wicklow 

 have been identified by the late Prof. 

 Boettger as JIargaritana pyrenaica 

 Locard. Seemingly scarcer than in 

 former times in many rivers, perhaps 

 owing to the depredations of the pearl- 

 searchers and their' wanton destruction. 



Anodonta cygaea iLinue). 



JL/ti/us cygneus, Brown, Mem. Werner. 

 Soc, vol. ii, p. 515, 1818. Anodon 

 cygneus, Thompson, Cat. L. & F. "W. 

 Moll, of Ireland, p. 40, 1840. 



WD ED LD AN 

 FE TY AR DO 

 WMSL LE MO 



EM RO CV LH 

 WC NG LF WH ME 



SG EC KD DU 

 CL NT QC CW wi 



NK LK ST KK WX 

 SK MC EC WA 

 WC 



This bivalve has a somewhat similar 

 range to Planorhis vortex and Neritina 

 Huviatilis, but is more widely distributed 

 in the north and north-east, occurring 

 in Lough Ncagh and the neighbouring 

 districts of Antrim, Down, and Armagh. 

 It reaches the west coast at Westport, 

 in West Mayo, where a small, tumid 

 form is common in the Carrowbeg. 



