554 CAMBRIAN BRACHIOPODA. 



by figures If, lo-s. With growth in size and age the shell increases in thickness notably over the 

 posterior portions. 



In some notes [1901, p. 692] on "Lingulepis gregwa" (Matthew), I identified this shell as 

 "Oholus (Lingulepis) gregwa." It is closely related to it but difl^ers in the surface characters. 

 The exterior shell of LinguleUa (Lingulepis) gregwa is marked by fine, irregular, elevated, and 

 sometimes inosculating ridges that have a row of minute tubercles on them that give a beaded 

 appearance to each ridge. The surface of the shell of L. (L.) exigua has a much more minutely 

 granulose surface formed by very irregular, inosculating, elevated lines or ridges, much like 

 that of L. (L.) roherti (Matthew). 



Matthew [1903, p. 193] refers this form to "Lingulepis starri var." With the types of 

 slarri as a basis of comparison I find that the type of surface of starri is as stated by Matthew 

 [1891, p. 147]: "Each valve is ornamented by numerous, concentric furrows, closely set, about 

 12 to 15 to a millimeter." I find 8 to 10 on one of the typical specimens. This surface is quite 

 unhke the surface of L. (i.) exigua which is as described above. Wlaen the thin outer layer is 

 exfoliated the concentric striae and ridges of growth are like the surface of starri, but the outer 

 surface is roughened ("granulated," Matthew) in a manner unlilve the surface of L. (L.) exigua. 

 It has the appearance under a strong magnifier of a surface produced by fiae points distributed 

 over an incrusting layer of shell. 



Formation and locality. — ITpper Cambrian: (3n) Thin-bedded sandstone on Salmon River, Gillis Hill, 13 miles 

 (20.9 km.) south of Marion Bridge, eastern Cape Breton, Nova Scotia. 



Middle Cambrian: (3i) Compact, fine-grained, thin-bedded, gray sandstone of the Paradoxides zone [horizon of Division 

 C&h, Mattheio, 1903, p. 195], on McLean BrooTc, 1 mile {1.6 km.) east of McCodrum Brooh and 1.5 miles (2.A hm.) west 

 of Marion Bridge; (10s and lOt) sandstone on McLean Brook, near Marion Bridge; (307f [Matthew, 1903, p. 198]) shale 

 of Division C2a on McLean Brook, Mira River; (307g [Matthew, 1903, pp. 195 and 198]) shales of Division C2b on 

 McLean Brook, Mira River; (13r) sandstone of the "Johannian" Division of Matthew's section on Gillis Brook, Bast 

 Bay, east of Bras d'Or Lake; and (llz) sandstone on Big Ridge, 2 miles (3.2 km.) south of Marion Bridge, on the 

 canal of John McDougald; all in eastern Cape Breton, Nova Scotia. 



, LiNGXJLELLA (LiNGULEPIs) GREGWA (Matthew) . 



Plate XLIV, figures 1, la-p. 



Idnguklla gregwa Matthew, 1899, Bull. Nat. Hist. Soc. New Brunswick, vol. 4, pp. 199-200, PI. I, figs. la-f. (De- 

 scribed and discussed as a new species.) 



Oholus {Lingulepis) gregwa Walcott (in part), 1901, Proc. U. S. Nat. Mus., vol. 23, pp. 692-694. (The following 

 species were included under LinguleUa (Lingulepis) gregwa in this reference; LinguleUa (Lingulepis) exigua, 

 L. (L.) gregwa, LinguleUa tumida, and L. atava. The specimens upon which the description was based are now 

 referred to LinguleUa (Lingulepis) exigua. 



Lingulepis gregwa Matthew, 1903, Geol. Survey Canada, Rept. Cambrian Rocks Cape Breton, pp. 56-57. (Notes 

 on orientation of shells.) 



Lingulepis gregiva Matthew, 1903, idem, pp. 126-131, PL IX, figs. 3a-f. (Described and discussed. Figs. 3a-f are 

 copied from Matthew, 1899, PL I, figs, la-f.) 



The description of LinguleUa (Lingulepis) exigua (Matthew) applies very closely to this 

 species, with the exception of the surface characters and details of outline, and the interior 

 markings of the valves. As a whole, the ventral valve of L. (L.) gregwa is less acuminate, 

 and the outline of the dorsal valve is more rounded posteriorly. A comparison of the series 

 of illustrations of the two species fully exliibits the differences referred to. The exterior sur- 

 face of the shell of L. (L.) gregwa is marked by a few, strong, concentric lines of growth, and 

 numerous fine, concentric, irregular, often inosculating ridges having a row of minute tubercles 

 on them that gives a beaded appearance to each ridge. This appearance is unmistakable when 

 the outer shell is at all weU preserved. There are also indications of very fine radiating ridges, 

 irregularly dispersed over the surface of the shell. Wlien the thin, higlily ornamented outer 

 layer is exfoliated the various lamellse of the shell show very fine, radiating strise, and a few 

 concentric lines of growth. The interior of the shell has rather large scattered punctse, and 

 occasionally a specimen shows the punctae gathered in concentric lines. The shell is built up 

 of a thin outer layer and several inner layers, or lamellae, that are more or less obfique to the 



