EDMONDIA PRIM^EVA. 307 



front, but becoming less well marked posteriorly, with here and there a deeper- 

 concentric groove. Shell of moderate thickness. 



Dimensions. — Fig. 2, Plate XXX. The type of M' Coy's Lutraria prisca 

 measures — 



Antero-posteriorly . . . .97 mm. 



Dorso-ventrally . . . .64 mm. 



Elevation of valve . . . .20 mm. 



Localities. — England : the Carboniferous Limestone of Castleton and Thorpe 

 Cloud, Derbyshire. Scotland : Lower Limestone series of Langside, Beith ; 

 Cousland, near Edinburgh. Ireland : the Carboniferous Limestone of Millicent, 

 Clane, co. Cork ; Doohybeg, co. Limerick. 



Observations. — The original specimen of Lutraria primseva, Portlock, has 

 disappeared, but the figures and description afford sufficient evidence of the 

 characters of the species. Apparently another shell has been placed in the 

 collection under the name, which belongs to quite a different genus, and this 

 quite accounts for the fact that Mr. Etheridge (op. supra cit.) refers Portlock's 

 shell to the genus Myacites. 



M'Coy considered that his Lutraria prisca was less transverse that L. primseva, 

 and that the ventral margin was more convex, which is true for the type, which 

 was a much larger example than that of Portlock. When, however, the lines 

 marking the several stages of growth are examined in the shells with a flattened 

 ventral border, it is seen that when young and in the immature stage the ventral 

 border was very much rounded, and the flattening only occurs later on ; and it is 

 to be noted also that this flattening of the ventral border is accompanied by a 

 compression of the valves, as if regular growth had been in some way interfered 

 with. Unfortunately, I have not a large number of examples to study, but 

 specimens with and without a flattened lower border occur together in the same 

 beds, and the latter never exhibit the irregularities of growth. I have, therefore, 

 considered M'Coy's species to be synonymous with the Edmondia prim&va, 

 Portlock, sp. 



De Koninck has adopted M'Coy's specific name without any reference to 

 Portlock's specimen. He describes three other species which I think must be 

 regarded as synonymous. Broeclda latissima is said to differ from B. prisca " par 

 sa moindre epaisseur, par sa difference dans les rapports entre la hauteur et la 

 largeur et par ses crochets plus anterieurs." 



The dimensions of B. latissima are given as : length 106 mm., height 71 mm. ; 

 that of B. prisca, from a very imperfect example : length 95 mm., height 64 mm. ; 

 which are at once seen to be very fairly identical. B. Kayseri is said to differ in 

 the same character from B. latissima, the dimensions of the former being; length 

 95 mm., height 60 mm. Of B. normalis he remarks, " Le Broechia normalis a une 



