BRACHIOPODA. 177 



SiPHONOTRETA (?) MiNNESOTENSIS, Sp. IIOV. 

 PLATE IV, FIGS. 37, 3S. 



Shell subovate in outline. Pedicle-valve more convex than the brachial, slightly 

 flattened along the median line, sloping with equal convexity toward the 

 lateral and anterior margins. Foramen apical (?). Brachial valve depressed- 

 convex, somewhat elevated about the umbo. Surface covered, in the um- 

 bonal region, with line, anastomosing and gently undulating concentric lines, 

 which, in the later portions of the shell, are finely granulose or serrated ; at 

 about one-third the length of the shell coarser varices of growth appear, 

 between which the finer lines are retained. Surface covered with hollow 

 spines of various sizes, which appear to have been most closely set over the 

 umbonal region of the pedicle-valve. Here, where the growth-lines are 

 absent, the spine-bases in the original specimen are large and all of about 

 the same size and are disposed without order. Over the other portions of 

 the shell the spines are set along the edges of the varices, small and large 

 being indifferently mixed. The bases of the spines make annular swellings 

 on the interior of the valves. The length of the original specimen is 15 

 mm., width, 12 mm. 



Trenton limestone. Minneapolis, Minnesota. 



Orbiculoidea (Schizotreta) ovalis, sp. nov. 



PLATE IV E, FIGS. 4, 5. 



Shell subelliptical in outline. Valves with apices situated a little behind the 

 center. Lower valve with the apex erect or inclined slightly forward. Ex- 

 ternal foraminal groove narrow, extending for about one-half the posterior 

 radius of the valve. Surface about the foramen convex, but elsewhere slightly 

 depressed in its slope from apex to margin. Upper valve more elevated than 

 the lower, apex inclined backward, posterior slope gently concave. Surface 

 marked by elevated nearly equidistant concentric striae. Shell-substance 

 thick, the inner laminae showing fine radiating lines over the anterior region. 

 Length of the original specimen, 8 mm., width, 6 mm., thickness through 

 the apices of the conjoined valves, 3 mm. 



Trenton limestone. Middleville, N. Y. 



