740 CAMBRIAN BRACHIOPODA. 



toward the cardinal margin, and in other shells they are clearly dej&ned all over the surface ; 

 the increase in niunber is by bifurcation and interpolation; fine, threadlike concentric striae 

 and strong squamose lines of growth cross the ribs. 



Ventral valve moderately convex, with the umbo and apex slightly ciurved over the area 

 (PL XCIX, fig. 1), or erect above the area (PI. XCIX, fig. lb). The cardinal area appears to be 

 shghtly concave; divided midway by a triangular delthyrimn, which is more or less closed by a 

 concave plate that Hall and Clarke consider [lS92c, p. 231] to be formed by the extension of the 

 dental plates or lamellae; from the casts it appears that the teeth were well developed and sup- 

 ported by dental plates that miited at the center opposite the delthyrium, but did not reach the 

 bottom of the valve or a median septum; the free spondylium, varied in length from a narrow 

 rim opposite the head of the delthyrium to a plate two-thirds or more of the length of the 

 delthyrium. 



Dorsal valve imiformiy and moderately convex, with the apex curved over to the edge of 

 the low area; area divided by a broad delthyrium; casts of the interior show that the cruras 

 were strong, dental sockets shallow, and that the crural plates extended across the umbonal 

 cavity, imiting to define what may be called a pseudocruralium. No trace of a cardinal process 

 has been seen in a large number of casts of the interior, and Hall and Clarke did not find any 

 in a large amornit of material. 



The casts of the mterior show that the inner' layer of the shell was minutely punctate, and 

 a shell preserving some of the inner layers has every appearance of such a structure. 



Observations. — This species differs from all recognized species of the genus by its surface 

 ribs and strise. 



The specific name was given in honor of Mr. E. Billings. ' 



Formation and locality. — Middle Cambrian: (3e) Shale 25 feet (7.6 m.) above the basal quartzite, on Seeley 

 Street, St. John; (3b) shale at the base of the Paradoxides zone, at the head of Seeley Street, St. John; (301k) St. John 

 formation in the city of St. John; (301g) sandstones of Di\'ision Ic of Matthew, at Portland (now a part of the city o 

 St. John); (308h and 308i) shales in Portland (now a part of the city of St. John); (SOlj) shales of the St. John formation 

 at Ratcliffs Millstream; and (21 and 2m) limestone at the base of the Paradoxides zone [Matthew, 1895a, p. 108], on Han- 

 ford Brook; all in St. John County, New Brunswick, Canada. 



PrOTOETHIS HELENA Walcott. 



Plate XCIX, figures 4, 4a-b. 



Protorthis helena Walcott, 190.5, Proc. U. S. Nat. Mus., vol. 28, p. 282. (Characterized and discussed essentially as 

 below as a new species.) 



This species is founded on the cast of a ventral valve associated with Trematoholus Tcemfanum 

 (Matthew) . The form of the spondylium and area is much like that of Protorthis latourensis 

 (Matthew) (PI. XCIX, figs. 3b and 4b), but the smooth shell with its broad, romided mesial 

 sinus is tmlike that species and also other species of the genus. The shell appears to have 

 been thicker than that of P. latourensis. Only traces of growth lines are preserved on the 

 cast. The ventral valve is 10 mm. long, with a width of 14 mm. The cast shows that the teeth 

 and dental plates were unusually strong. 



This species differs from all others of the genus by its smooth or nearly smooth siirface and 

 strong median sinus. It suggests Sijntrophia harabuensis (Winchell) at first sight, but there is 

 no evidence of a median septum supporting the spondyhum. 



The specific name was given for IVirs. Walcott, who collected the specimen. 



Formation and locality. — Middle Cambrian: (2u) Lowest beds exposed on the south side of Long Island, Ken- 

 nebecasis Bay [Matthew, 1898a, pp. 124 and 127], St. John County, New Brunswick, Canada. 



Protorthis ? hunnebergensis Walcott. 



Plate XCV, figures 5, 5a-c. 



Protorthis f nunnebergensis Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 284. (Described and discussed as on p. 

 741 as a new species. The name "nunnefcer^ensis" was used under the impression that the correct spelling of 

 the type locality wds Nunneberg; the species occurs on Hunneberg.) 



