O'Meara — Hejiorf on the Irish Diatomacece. 325 



attenuated towards the ends ; stri^ linear, fine ; slightly radiate ; not 

 quite reaching the median line, but terminated by two strongly 

 developed sulci, which bend in slightly towards the central nodule at 

 either end, leaving a narrow lanceolate space about the median line 

 free from striae. 



Smith and Grunow, the former doubtfully, regard this form as 

 identical with ISTavicula meleagris, Kiitz. Bac, p. 92, T. xxx., fig. 37. 

 Eabenhorst, however, regards Kiitzing's form as distinct from the 

 present ; and in this I am disposed to agree with him, as I have seen 

 specimens exactly corresponding with that of Kiitzing, and as I think 

 quite distinct from Mastogioia lanceolata. 



Wm. Sm., B. D., Vol. ii., p. 64, PI. liv., fig. 340. The figure 

 and description are correct, as far as they go, but neither the longi- 

 tudinal sulci about the median line, nor the strise are described. 

 Ealfs, in Pritch., p. 924. Grunow, Verhand. der Zool. Bot. Gesel., 

 Band x. 1860, p. 576. Heiberg, De Danske Diat., p. 94. Eab. PL 

 Eur., sect. 1, p. 261. Cleve, Om Svenska och Norska Eiat., p. 230. 



Tacumshane, Co. "Wexford. Lough Gill, Co. Kerry. Salt marsh, 

 Kilcool, Co. "Wicklow. Salt marsh near the town of Galway. P)olly- 

 mount Strand, Co. Dublin. 



Mastogioia convergens, !N". S. Marine or brackish water. 



Yalve broadly elliptical; length -0018; breadth -0008; rounded 

 at ends ; median line straight, strongly marked, and of equal breadth 

 throughout ; central nodule small and round : marginal plates broad 

 in the middle, gradually attenuated towards the ends, at some dis- 

 tance from which they bend outwards ; the space between the plates 

 is broadly lanceolate at either end, and narrower in the middle, where 

 the boundary line curves very gently towards the margin ; loculi 

 broader than in the last ; strife fine, linear, convergent in the middle 

 of the valve, where they are stronger and farther apart, and for the 

 remainder gently radiate. (PI. 29, fig. 9.) 



On first ^dew, this form might readily be confounded with the 

 preceding ; but the more carefully it is examined, the more apparent 

 are its distinctive characteristics. In its outline, it is broader for the 

 length than Mastogioia lanceolata ; its ends are broader, and more 

 round. In the latter, the loculi are more numerous, shorter in the 

 middle, and gradually diminishing towards the ends ; in the present 

 case, the loculi are wider in the middle, and suddenly become attenu- 

 ated towards the ends. The longitudinal sulci near the median line, 

 so marked a feature of M. lanceolata, are wanting in this. In M. 

 lanceolata, the strise are uniformly radiate ; in M. convergens, they 

 are convergent in the middle, and for the rest more decidedly radiate 

 than in the other. 



Salt marsh near' the town of Galway. Lough Gill, Co. Kerry, 

 accessible to the tide. 



