20 LINNARSSON, BRACHIOPUDA OF THE PARADOXIDES BEDS. 



tunity of examining. Not quite so well do the interiörs of tlie 

 dorsal valve agree, but tlie differences may depend only on in- 

 dividual variations and, perliaps, also on the mode of preserva- 

 tion. The greatest difFerence seems to be in the shape of the 

 longitudinal ridges. The two lateral ones are not mentioned by 

 ]\Ir. Dayidson, but they are indicated b}' the branches figured 

 behind the anterior muscular scars. In the Scandinavian speci- 

 mens examined by me the lateral ridges are more separated 

 from the mesial one, and not so small in comparison with it. 

 The circumstance that the anterior muscular scars have not been 

 observed in the Scandinavian specimens cannot be considered as 

 proving a real diversity, as that circumstance must be owing to 

 the mode of preservation. 



Acrothele n. g. 



Shell corneous, composed of several lamina, the inner smooth 

 and polished, the outermost one rough and opaque. Yentral valve 

 slightly conical, with excentric umbone, pierced by a minute 

 ibramen, in front of which there are. at Icast in one species, two 

 small "wart-like protuberances ; the field between the umbone and 

 the posterior margin is usually a little flattened, thus Ibrming a 

 slight indication of a false area. Dorsal valve with marginal 

 umbone, consisting of two wart-like protuberances. In the in- 

 teriör of the dorsal valve there are two oblong, diverging mu- 

 scular scars close to the posterior margin, and two small, rounded 

 scars near the middle. The muscular scars are separated by a 

 longitudinal ridge. 



The above generic description is chiefly founded on one of 

 the two species found, as I have not had any opportunity of 

 examining the interiör of the other, of which the materials have 

 been imperfect also in other respects. The two species are, 

 however, so similar in general shape that it is probable that the 

 inner cliaracters also are much the same. The most nearly re- 

 lated genera are, 1 think, Obolella and Acrotreta. The former 

 differs, according to the generic description given by Mr. BiL- 

 LIXGS, by having the shell calcareous, though I think that species 

 with corneous shell substance have, by some authors, been also- 

 referred to this genus. Of Acrotreta the interiör is nearly unknown. 

 In external cliaracters it has many undeuiable affinities to Acro- 

 thele. Thus they have both the dorsal valve flattened, with mar- 



