ACROTRETIDiE. 653 



(43) Shales on the summit of Moses Hill, 2 miles (3.2 km.) west of North Greenwich; and (338i) shales 1 mile (1.6 

 km.) west-northwest of South Argyle; both near the line between the Schuylerville and Cambridge quadrangles (U. S. 

 Geol. Survey), Washington County, New York. 



(338z) Limestone on the north side of Bald Mountain, about 2 miles (3.2 km.) northwest of Greenwich, Schuyler- 

 ville quadrangle (U. S. Geol. Survey), Washington County, New York. 



ACROTHELE PRIMA (Mattliew). 

 Plate LXI, figures 6, 6a-b; Plate LXII, figure 2. 



Acrothele matthewi prima Matthew, 1886, Trans. Roy. Soc. Canada for 1885, 1st ser., vol. 3, sec. 4, No. 4, p. 41, PL V, 



figs. 16 and 16a. (Characterized. The specimen represented by figs. 16 and 16a is redrawn in this monograph, 



PI. LXI, fig. 6.) 

 Acrothele ■matthewi prima Matthew, Hall and Clarke, 1892, Eleventh Ann. Rept. State Geologist New York for 1891, 



PL III, fig. 27. (Fig. 27 is drawn from the specimen represented in Matthew, 1886, PL V, figs. 16 and 16a.) 

 Acrothele matthewi prima Matthew, Hall and Clarke, 1892, Nat. Hist. New York, Paleontology, vol. 8, pt. 1, PL III, 



fig. 25. (No text reference. Fig. 25 is copied from fig. 27 of the preceding reference.) 

 Acrothele matthewi prima Matthew, 1895, Trans. New York Acad. Sci. for 1894-95, vol. 14, PL V, figs. 7a-b. (No text 



reference. The figures are drawn from the specimen represented in Matthew, 1886, PL V, figs. 16 and 16a.) 

 Acrothele matthewi prima Matthew, 1902, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pt. 5, No. 20, pp. 397 and 402, 



PL XVII, figs. 4a-b. (Mentioned. The figures are copied from figs. 7a-b, respectively, of the preceding 



reference. ) 

 Acrothele matthewi prima Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, p. 104, PL V, 



figs. 4a-b. (Mentioned. Figs. 4a-b are copied from Matthew, 1902a, PL XVII, figs. 4a-b, respectively.) 

 Acrothele matthewi Grabau and Shimer (in part), 1907, North American Index Fossils, vol. 1, p. 200, fig. 234g (not 



234f). (Described. Fig. 234g is copied from Matthew's figure, 1895a, PL V, figs. 7a-b, of Acrothele matthewi 



prima. The specimen represented by fig. 234f belongs with Acrothele matthewi, which see, p. 648.) 



This species is distinguished from Acrothele matthewi (Hartt) by the apex of the ventral 

 valve being almost directly over the posterior margia instead of from one-fifth to one-sixth the 

 length of the valve from it. It has a finely granulated surface of the same type as that of 

 A. matthewi and the valves are similar in outline except near the apex of the ventral valve. 

 The average size of this species is a little less than that of A. matthewi. 



The variety costata was separated by Matthew [1895a, p. 128] on account of the presence of 

 six or more ribs; this character is an exceedingly variable one and of little value, as the ribs 

 vary from a faint trace to twenty or more ribs, but as it has been used the varietal name is 

 retained. 



Formation and locality. — Middle Cambrian: (2g)a Sandstones of Division Ihl; (2f) sandstones 3 feet below 

 2g in Division Ibl; (2h) sandstones of Division lb2; and (2i) sandstones of Division lb3; all in Matthew's [1895a, p. 

 108] Protolenus zone, Hanford Brook, St. John County, New Brunswick. 



(13t) Sandstones at the base of Division Elb; and (13d") sandstones 10 feet (3 m.) below Division E2a; both in 

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



Acrothele prima costata (Matthew). 



Plate LXI, figures 4, 4a-d. 



Acrothele matthewi costata Matthew, 1895, Trans. New York Acad. Sci. for 1894-5, vol. 14, p. 128, PI. V, fig. 9. 



(Characterized as a new variety.) 

 Acrothele matthewi costata Matthew, 1902, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pt. 5, No. 20, p. 397, PL XVI, 



fig. 6. (Mentioned. Fig. 6 is copied from fig. 9 of the preceding reference.) 

 Acrothele matthewi costata Matthew, 1903, Geol. Siu-vey Canada, Rept. Cambrian Rocks Cape Breton, p. 104, PL IV, 



fig. 6. (Mentioned. Fig. 6 is copied from Matthew, 1902a, PL XVI, fig. 6.) 



Matthew [1895a, p. 128] separated this variety on account of the presence of six or more 

 broad, radiating ribs that are not continuous, but that are interrupted by some of the strong 

 lines of growth; the ribs do not occur on very young shells or near the umbo of the old shells. 

 The surface of the epidermal layer is granulated in the same manner as the typical forms of 

 A. matthewi (Hartt). 



a 2g is the type locality, though the specimens in the United States National Museum collections to which that number is assigned were 

 collected later than the type specimens. 



