No.ijyy. CAMBRIAN BRACHIOPOD A— WALCOTT. 589 



shows a broad, short median ridge posteriorly that extends beyond 

 the center of the valve. 



Ohservations. — This species appears to be a true Acrotreta with the 

 apical callosit}' elongated by the elongation of the pedicle valve. The 

 brachial valve is more convex than in most species of Acrotreta^ which 

 gives a stronger relief to the ridges on the cast between the cardinal 

 scars and the median ridge. The posterior view should be compared 

 with the same view of the brachial valve of Acrotreta i<(igittalh and its 

 varieties. The fretted surface is of the same type as that of several 

 other species of the genus. 



Dr. G. F. Matthew had very little material when he described the 

 species; subsequently he created the variety* ovalis. from a more elon- 

 gated pedicle valve. In the collection made for the U. S. National 

 Museum by Mr. S. \A'ard Loper there are a number of pedicle and 

 brachial valves. The range of variation in outline appears to cover 

 the variety ovalis. Some are more transverse than the original type 

 of the species, and others nearh' as elongate as the variety ovalis. 1 

 have therefore considered the varietv as within the original species. 

 Some of the shells .show elongation, and others are broadened by 

 distortion. 



Dr. G. F. Matthew called attention to the resemblance of this species 

 to Linnarssonia and Acrotreta^ and when describing the genus Acro- 

 tliyra suggested that it might belong to that genus. It appears, how- 

 ever, to be a true Acrotreta. A series of specimens supplemented by 

 the types and a number of pedicle valves received from Dr. Matthew, 

 which he had provisionally identilied as '''Acrotreta gemma Bill?,"^ 

 show a rather remarkable variation in outline and position of the apex 

 of "the pedicle valve. The narrow forms, var. oralis Matthew, have 

 the apex extended be3-ond the posterior margin, and in the broad forms 

 the apex is above or in advance of the posterior margin, but if the 

 shells are compressed vertically the apex may be pushed out over the 

 false area whether the shell be narrow or broad. I think that in the 

 normal form the false area is vertical or slightly inclined backward. 



Formation and locality. — Middle Cambrian, division lb of Mat- 

 thew's section, Hanford Brook. New Brunswick. 



ACROTRETA KUTORGAI, new species. 



The external characters of the pedicle valve are clearly exhibited, 

 and what is known of the interior, by a unique specimen, as it is the 

 only one known to me that clearh- shows the true area and pseudo- 

 deltidium of the pedicle valve. The corresponding portion of the 

 brachial valve is well defined in the casts. The median ridge is as 

 long proportionall^v as that of A. hisecta. and, like it, varies in length 

 and size in different shells. 



1 Trans. X. Y. Acad. Sci., XIY, 1895, p. 126. 



