364 S. W. Ford—Forms of Brachiopoda. 
Art. LIL—On certain Forms of Brachiopoda oceurring in the 
Swedish Primordial; by S. W. Forp. 
; ing to M. Linnarsson’s 
description, in the absence of the longitudinal *slit of Discina, 
the perforation of the apex of the ventral valve, and in its inte- 
rior markings so far as these have been made out. The shell 
substance is corneous. . Linnarsson considers the most 
nearly related genera to be Obolella and Acrotreta, but at the 
acea the presence of an umbonal orifice is always readily recog- 
nizable. The interior of this valve, so far as known, shows 00 
trace whatever of muscular scars or imprints. 
In that subdivision of the American Primdedial known as the 
Lower Potsdam, and which is considered to lie above the Para- 
dowides-bearing strata of this continent, we have at Troy, N. Y.,a 
species of Lingulella (L. coelata), very closely resembling in the 
interior markings of its dorsal valve the dorsal valve of Linnars- 
son's A. coriacea, and in the same formation, both in New York 
and Canada, another form bearing an equally strong resemblance 
to his A. granulata. This latter American form is the operculum 
gy a Pt i. Its true character was first ascertained by Mr. 
illings, who described it, together with the shell to which it 
belongs, in the Canadian Naturalist for December, 1871, under 
the name of Hyolithellus micans.+° It is usually circular in 
31, Om faunan ilagren med Paradomides dlandicus;” af G. Linnarsson. pines 
‘oreni -i Stockholm Farh Als. o. . 
¥ Boo alao this Journel for May,1872. CR penne 
