RHYNCHONELLIDiE. 



165 



Obs. Although some uncertainty seems to have prevailed amongst palseontologists as 

 to the genus to which Dalman's species should be referred, all the evidence in my 

 possession would tend to confirm its position in the genus Rhynchonella. The form 

 of the shell is very like that of several well-known species of the genus, such as 

 Rh. angulata, Linn., &c. When quite young (fig. 11) there is no apparent mesial fold, 

 the dorsal valve being depressed along the middle, with interspaces of equal width betw^een 

 the ribs. The foramen also is then contiguous to the umbone of the opposite valve, while 

 the narrow deltidial plates which margin its lateral portions are disunited in the middle ; 

 but as the shell acquires age the mesial fold becomes developed, and the beak more or 

 less elongated, so that the foramen is in many specimens at a considerable distance from 

 the hinge-line, as seen in figs. 7, 9, 10. At page 276 of vol. ii of the ' Pal. of New York,' 

 Prof. Hall remarks that this species presents considerable variety of form and proportions. 



It appears difficult to make out whether it was Dalman or Hisinger who first gave 

 the name of cuneata to this species. Dr. Lindstrom thinks it w^as the latter, as in the 

 'Bidrag til Sveriges Geognosi,' part iv, p. 239, he mentions Terebratula cuneata, D., and 

 gives a drawing of it in his pi. vi, fig. 8. The D. evidently means Dalman ; but if the 

 memoir of Dalman had been then published Hisinger would have cited the plate and 

 figure of the last-named author. It is probable that Hisinger had seen Dalman's 

 manuscript, which was ready in 1827, but not published until 1828. However, it is 

 also strange to find in Dalman's memoir, ' K. Vet. Akad. Handl.,' p. 141, the species 

 referred to as Hisinger's, while in the ' Lethaea Suecica ' Hisinger again restores it to 

 Dalman. The only way I can see to settle the authorship will be to assign it to both. 



I do not know what to make of M'Coy's Atrypa sexcostata (' Synopsis Sil. Poss. of 

 Ireland,' p. 41, pi. iii, fig. 30, and fig. 13 of our Plate), which is stated to be "Trian- 

 gular, depressed ; front subtruncate, sides straight, margin very obtuse ; surface with 

 six angular radiating ribs. Loc. — Lettershanbally, Leenane, County Galway, and in the 

 sandstone of Shanballymore, Oughterard, County Galway, Ireland." I have seen the 

 original specimen, kindly lent to me by Sir R. Griffith ; it is an obscure fragmentary 

 fossil, and may, perhaps, be an imperfect specimen of Rh. cuneata. 



Position and Locality. Rh. cuneata occurs in the Llandovery rocks, but principally 

 in the Wenlock limestone. In the Woolhope limestone of Hay Head, near Walsall ; 

 Wenlock hmestone and shale of Dudley, Benthall Edge, Lincoln Hill, &c. ; Canvvood 

 and Dormington Wood, Woolhope ; Hill End and Callow Parm, Abberley ; Rock Parm, 

 May Hill. 



In Scotland it is found in the shape of imperfect casts in the Llandovery rocks of 

 Ardmillan, Thrave, and Mullock Hill, in Ayrshire ; but I am not certain that the identifi- 

 cation is correct. 



In Ireland M'Coy mentions Shanballymore, Oughterard (Sir R. Griffith's Collection). 

 It is common in the Island of Gothland. It was also found by Barrande in the 

 Silurian rocks of Bohemia. D'Eichwald quotes it from the banks of the River 



