BRACHIOPODA. 119 



At present we can safely refer to Eumetria only the American forms, E. vera 

 and var. costata, Hall, and E. Vernmiliana, Hall, from the Kaskaskia and Warsaw 

 limestones of the lower Carboniferous series, which are, perhaps, all repre- 

 sentatives of the same species. Of other finely striated species which may 

 prove congeneric, is the Retzia serpentina, de Koninck,* but all the Carboniferous 

 species with REXziA-like exterior will need most careful scrutiny before their 

 generic values can be determined. 



Genus ACAMBONA, White. 1862. 



PLATE LI. 



I860. Retzia, Swallow. Trans. St. Louis Acad. Sci., vol. i, p. 653. 



1862. Aeamhona, Whitb. Proc. Boston Society Nat. Hist., vol. ix, p. 27, figs. 1, 2. 



This name was proposed for a large species described as Acambona prima, and 

 its generic characters were given in the following language : 



" Shell of the general appearance and surface characters of Retzia ; furnished 

 with internal spires, pointing outward and downward ( ? ). Beak of ventral 

 valve prominent, incurved, pointed ; area emarginate in front, or V-shaped, 

 reaching to the point of the beak, and extending forward of the beak of the 

 dorsal valve on each side of it. Beak of the dorsal valve closely incurved, fill- 

 ing, or nearly filling the forked space or emargination in the front part of the 

 area, being itself without angular, hinged extensions, or area, to meet that of 

 the opposite valve." (White, he. cit.) 



Specimens of this species are quite rare, and we have seen none in which 

 the beak is perfectly retained. The structure of the beak and the absence of 

 a foramen, as given by White, seem unnatural for a member of these retziiform 

 shells, and in view of the author's statement (p. 28) that his figures are to some 

 degree restorations, this point will require careful re-examination. Nevertheless 

 the species A. prima bears an internal pedicle-tube, as in Retzia and Hustedia, a 

 character absent in Edmetbia, while the exterior characters of the shell are 



* Thip S|>ecies is referred to the genus Acamboka in db KoNrNCK's last woik on the Faune du Calcaire 

 Carbonifere de Belgique ; Brachiopodes, Explic, pi. xxii, figs. 25-31, 1889. Most of the figures given in 

 this work, however, show a vei-y clearly developed foramen, on the absence of which the genus Acambona 

 was based. Waaobs, on the other hand, has more recently suggested that this rare species may prove con- 

 generic with his Uncinella iTidica. 



