BILLINGSELLID^. 743 



Observations. — Doctor Matthew very kindly sent me his types of this species and I have 

 had a number of drawings made from them. A glance at them and the illustrations of P. 

 billingsi shows that the two species are quite distinct and that P. quacoensis is unlike any other 

 shell referred to the genus. 



As far as seen, the free spondylium of the ventral valve is short ; the teeth are clearly shown 

 in the cast. The pseudocruralium of the dorsal valve is much more clearly defined than in 

 P. billingsi (pc, PI. XCIX, figs. 2c. and 2e), the area is higher (Pi. XCIX, fig. 2c), and traces of 

 the adductor muscle scars are preserved (PI. XCIX, fig. 2d). 



Formation and locality." — Middle Cambrian: (301m [Matthew, 1886, p. 44]) Shale of Division Ic of Matthew's 

 section on Porters Brook, St. Martins; (3b) shale at the base of the Paradoxides zone, at the head of Seeley Street, St. 

 John; (301w) shales of Division lc2 of Matthew's section at Portland (now a part of the city of St. John); and (301g 

 [Matthew, 1886, p. 44]) sandstones of Division Ic at Portland (now part of the city of St. John); all in St. John County, 

 New Brunswick, Canada. 



Protorthis wingi Walcott. 



Plate XCIII, figures 5, 5a-c. 



Protorthis wingi Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 286. (Described and discussed as below as a new 

 species.) 



General form transversely subelliptical. Surface marked by about 20 sharply ridged ribs, 

 with interspaces equal and usually greater than the width of the rib; shell with numerous 

 small and many larger and scattered punctse on the inner and outer surfaces. The largest 

 ventral valve has a length of 6 mm. ; width, 9 mm. 



Ventral valve convex, elevated at the umbo and beak; area high and divided midway by 

 a strong delthyrium, which is partly closed by a concave free spondylium (sp) as in P. bil- 

 lingsi; teeth strong, dental plates extended toward the center to unite and form the free 

 spondylium. 



Dorsal valve slightly convex, with a broad median sinus that is usually bounded by one 

 or two large ribs ; casts of the interior show a narrow area, broad delthyrium, and, opposite the 

 umbo, the cast of a small, broadly triangular, elevated area that probably served as the car- 

 dinal process for the attachment of the diductor muscles. 



Observations. — This species is most nearly related to Nisusia (Jamesella) nautes (Walcott) ; 

 it differs, as far as Icnown, in the character of the interior of the dorsal valve, the large punctae 

 scattered among the fine punctffi, and the sharp-ridged ribs. One cast of an interior of a ven- 

 tral valve (PI. XCIII, fig. 5a) appears to indicate that the shell was without the free spondyl- 

 ium; it not infrequently occurs in Protorthis billingsi (Hartt) that the free spondyhum is 

 reduced to a narrow rim about the margin' of the delthyrium and it may be that in this shell 

 it was absent. 



The specific name is given in memory of Kev. Augustus Wing, whose extensive, and excel- 

 lent work in the vicinity of Swanton, Vermont, was utilized by Billings and Logan in the reports 

 of the Geological Survey of Canada. 



Formation and locality. — Upper Cambrian: (28) Shales about 100 feet (30.5 m.) above the Olenellus horizon 

 south of Highgate Falls, 0.25 mile (0.4 km.) east of Swanton, Franklin County, Vermont. 



Protorthis sp. undt. Walcott. 



Protorthis sp. undt., Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 286. (Described and discussed as below as 

 an undetermined species.) 



Ventral valve convex, elevated at the umbo, apex incurved. The cast of the umbonal 

 cavity (pseudospondylium) indicates well-developed teeth and dental plates. On the cast six 

 radiating ribs occur in the distance of 1 millimeter; area about vertical. The surface of the 

 cast indicates that the interior layer of the shell was finely punctate. Length of valve 4.5 

 mm.; width, 5.5 mm. 



" Matthew does not state which of the two localities, 301g and SOlm, is the type, though he [1S86, p. 82] locates the type specimen (PI. XCIX, 

 fig. 2b) in Division Ic of his Etcheminian. * 



