720 CAMBRIAN BRACHIOPODA. 



Formation and locality. — Middle Cambrian: (13d") Sandstones 10 feet (3 m.) below Division E2a; (lOp) 

 sandstones just below the waterfall in Division E2b; and (3441 [Matthew, 1903, p. 90]) sandstones of Division E2e; all 

 in Matthew's [1903, p. 21] Etcheminian, Dugald Brook, Indian River, eastern Cape Breton, Nova Scotia. 



\ ACEOTHYEA SIGNATA PEIMA MattlieW. 



Plate LXXX, figiu-es 2, 2a-b. 



Acroihyra signata prima Matthew, 1902, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pt. 5, No. 20, pp. 382-383, PI. 



XIII, figs. la-g. (Described and discussed as a new variety. The specimens represented by figs, lb and Ic 



are redrawn in this monograph, PI. LXXX, figs. 2 and 2b, respectively.) 

 Acroihyra signata prima Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, p. 73, PL I, 



figs. la-g. (Text and figures copied from the preceding reference.) 



The material representing this shell is in poor condition, but sufficient evidence of the 

 form and interior characters of the ventral valve is preserved to show that it differs from 

 A. signata Matthew in its subconical form, and in the shorter and proportionally broader visceral 

 area. It is very difficult to find any clearly defined distinction between some specimens of 

 Acroihyra sera Matthew and A. signata prima, as the latter shows ventral valves quite as regu- 

 larly conical as the former. One of Matthew's type specimens shows a much higher apex on 

 the ventral valve than his figure 3c [1903, PI. I]; another with the apex broken off shows a 

 cast of the visceral cavity much like that in Plate LXXX, figure la (A. signata Matthew). 



Matthew [1902a, p. 383] found the types of this species in a fine gray shale interbedded 

 in the volcanic beds. The associated fossils clearly indicate that the fauna is essentially the 

 same as that which follows higher in the strata. 



Formation and locality. — Middle Cambrian: (13k) o Shales of Matthew's [1903, p. 15] Coldbrook, above the 

 great waterfall in Dugald Brook, Indian River, Cape Breton, Nova Scotia. 



Genus DISCINOPSIS Matthew. 6 



[3kKoc, quoit; and ^ip, face.] 



Discinopsis (Matthew MS.) Hall and Clarke, 1892, Eleventh Ann. Rept. State Geologist New York for 1891, pp. 

 250-251. (Described.) 



Discinopsis Matthew, Hall and Clarke, 1892, Forty-fifth Ann. Rept. New York State Museum for 1891, pp. 566-567- 

 (Copy of preceding reference.) 



Discinopsis Matthew, Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, pp. 105-106. (De- 

 scribed and discussed as a new genus.) 



Discinopsis Matthew, Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 4, PL XI, and pp. 142 and 146. (Classifi- 

 cation of genus.) 



All that is known of this genus is incorporated under the description of the type species. 

 Type. — Acrotreta? gulielmi Matthew. 



i, Discinopsis gulielmi (Matthew). * 



Plate LXXXII, figures 5, 5a-c. 



Acrotreta? gulielmi Matthew, 1886, Trans. Roy. Soc. Canada for 1885, 1st ser., vol. 3, sec. 4, No. 4, pp. 37-39, PL V, 

 figs. 14, 14a-e. (Described and discussed as a new species; see below for copy. The specimen represented by 

 figs. 14c and 14d is redrawn in this monograph, PL LXXXII, fig. 5. Figs. 5a-c of this monograph are drawn 

 from specimens in the type material, but none of them can be identified with Matthew's figures.) 



Discinopsis gulielmi (Matthew), Hall and Clarke, 1892, Eleventh Ann. Rept. State Geologist New York for 1891, 

 PL III, figs. 20 and 21. (Fig. 20 is drawn from the specimen figured by Matthew, 1886, PL V, figs. 14c and 

 14d. Fig. 21 is drawn from one of Matthew's type specimens, and the same specimen is redrawn in this mono- 

 graph, PL LXXXII, fig. 5a, but the specimen can not be identified with any of, Matthew's figures.) 



Discinopsis gulielmi (Matthew), Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, p. 105, 

 PL III, figs. 20-24. (Discussed. Figs. 20 and 21 are copied from figs. 20 and 21 of the preceding reference. 

 The remaining figures are drawn from specimens in Matthew's type material. Figs. 21, 22, and 23 represent 

 specimens which are redrawn in this monograph, PL LXXXII, figs. 5a (=21 and 22) and 5c (=23), but it is 

 impossible to identify the specimens with Matthew's figures.) 



The original description by Matthew follows: 



Shell subcircular in outline. Surface depressed-conical, apices eccentric, not marginal. Pedicle valve with 

 the apex truncated by a circular foramina! aperture (?). The interiorof this valve is characterized by a pan- of deep, 



a 13k is the type locality, though the specimens represented by that number in the United States National Museum collections were collected 

 later than the type specimens. 



!> Prioi to the definition of the genus Discinopsis the type species was referred to Acrotreta? [Matthew, 1886, p. 37]. 



