NO. 1395. CAMBRIAN BRACHIOPODA-WALCOTT. 295 



ribs are large on a prominent mesial fold; in most young- shells the 

 sinus and fold are inconspicuous, the convexity is ver}' moderate and 

 the shell smooth; nearly all the characters of the adult are missing. 



A group of young shells from Honej^ Creek shows only the smooth, 

 slightly convex forms with onl\^ slight ventral sinus and dorsal fold. 

 One larger shell associated with the young shells has a relatively deep 

 sinus and a trace of a plication. 



Formation and locality. — Upper Cambrian. Cold Creek Canyon 

 and Honey Creek. Burnet County. Texas. 



Genus POLYTOECHIA Hall and Clarke. 



Polytoechia Hall and Clarke, Pal. N. Y., VIII, 1892, Pt. 1, p. 239, pi. vii a, 

 figs. 26-30. 



Original diagnosis. — Shell small, t^ubtrihedral in contour. Hinge line straight, 

 about equaling the diameter of the shell. Pedicle [ventral] valve with a high, 

 nearly vertical cardinal area marked with oblique striations parallel to the lateral 

 margins. Delthyrium covered bj' a narrow, convex plate; the presence of a foramen 

 not determined. On the interior the <lental lamellfe are widely separated and 

 descend along the umbonal cavity for a short distance vertically, thence bending 

 sharply inward and meeting at a low angle in the median line, thus forming, with 

 the deltidium, a conspicuous subrostral vault. This inner spoon-shaped plate, 

 spondylium, is supported by a stout median septum, and two smaller lateral septa, 

 which meet at the lines of angulation; the former of these extends for the entire 

 length of the plate, while the latter is free from the accessory septa near its anterior 

 edge. The umbonal cavity of the valve is thus divided into five chambers, and in 

 the lateral chambers there is still another septum, lower than the rest and not 

 extending to the spondylium. The brachial [dorsal] valve is shallow and depressed- 

 convex, with a narrow cardinal area. The delthyrium is very broad, with a par- 

 tially developed covering, the dental sockets are widely separated, the crural plates 

 narrow and nearly parallel to the hinge line. The cardinal process is simple, linear 

 and quite prominent, and at its union with the crural plates is a subtriangular thick- 

 ening which is supported by a low median septum. Surface covered witli fine, ele- 

 vated radiating stria?, without evidence of median fold and sinus. 



Type.—Hemipronites apicalis, Whitfield. 



Ohservations. — This genus is known only in the Lower Ordovician 

 strata of Vermont and Montana. The tj^pe species is described as 

 having a convex deltidium covering the delthyrium of the ventTal valve; 

 this character and the additional septa supporting the spondjdium and 

 cruralium are the distinguishing characters between it and Syntrojjhia. 

 There is still less difference from Clitariihonites^ as in the latter the 

 convex deltidium is present. It is quite probable that representatives 

 of the genus will be found in the Upper Caml^rian formations when 

 they are searched more thoroughly. 



POLYTOECHIA ? MONTANENSIS, new species. 



This shell was placed with Camerella calcifera until sections were 

 made showing the numerous septa supporting the spondylium and 

 cruraliimi. In general form it is close to Syntrophia rotundata^ dif- 

 fering in the numerous supporting septa of the spondylium which 



