BRACHIOPODA. 44] 
Orthis (Dalmanella) testudinaria.] 
Minnesota, otherwise I do not see any difference between the two species. It is to 
be remembered, however, that the Nevada specimens do not show the cardinal area 
and that they are not quite as well preserved as the one you sent to me.” 0. ham- 
burgensis is found in the central part of the Pogonip group of Nevada, a horizon 
probably equivalent to the lower portion of the Chazy group of New York. The 
great difference, geographically and geologically, between the localities of O. ham- 
burgensis and the species here provisionally identified with it leads to the belief 
that the two may be specifically distinct. 
In Minnesota this form is found associated with O. testudinaria and is easily 
confounded with it. Upon examination, however, characters are noticed reminding 
one of O. tricenaria and other species referred to Orthis in its strict generic sense. 
The wide cardinal area, narrow delthyrium, simple cardinal process, and the fact 
that none of the striz terminate on the cardinal lines, are features of that genus. 
In O. hamburgensis the surface striz exhibit a strong tendency towards bifurcation 
and upon them are series of minute black spots, probably infillings of the puncte in 
the shell substance. Since Orthis is impunctate and always has simple plications, 
this species is better placed in Dalmanella. If this conclusion is correct, there is 
evidence to show that Dalmanella was derived from Orthis. 
Formation and locality.—Rare in the Trenton shales at St. Paul, near Cannon Falls, Lanesboro and 
Fountain, Minnesota. Also from the top of the Birdseye limestone near High Bridge, Kentucky. The 
typical specimens are from the central part of the Pogonip group of the Eureka District, Nevada, where 
the species is common. 
Collectors.—W. H. Scofield, E. O. Ulrich and the writers. 
Mus. Reg. No. 7897. 
OrtHis (DALMANELLA) TESTUDINARIA Dalman. 
PLATE XXXIII, FIGS. 17—22. 
1828. Orthis testudinaria DALMAN. Kongl. Svenska Vet.-Acad. Handl., for 1827, p. 115, pl. 11, fig. 4. 
1839. Orthis testudinaria CONRAD. Annual Report of the New York Geological Survey, p. 63. 
1842. Orthis striatula EMMoNs. Geology of New York; Report of the Second District, p. 394, fig. 3. 
1842. Orthis testudinaria? Emmons. Ibidem, p. 404, fig. 4. 
1847. Orthis testudinaria HALL. Palxontology of New York, vol. i, p. 117, pl. xxxnu, fig. 1; p. 288, 
pl. LX XIX, fig. 4. 
1856. Orthis testudinaria BILLINGS. Canadian Naturalist and Geologist, vol. i, p. 40, fig. 1. 
1858. Orthis testudinaria RoGERS. Geology of Pennsylvania, vol. ii, pt. ii, p. 818, fig. 601. 
1863. Orthis testudinaria BILLINGS. Geology of Canada, p. 165, fig. 144. 
1875. Orthis testudinaria? Wuirr. Report of the U. S. Geographical Surveys west of the 100th 
Meridian, p. 72. 
1875. Orthis testudinaria MILLER. Cincinnati Quarterly Journal of Science, vol. ii, p. 20. 
1882. Orthis testudinaria WHITFIELD, Geology of Wisconsin, vol. iv, p. 258, pl. xm, figs. 5-7. 
1888. Orthis testudinaria HALL. Second Annual Report, New York State Geologist, pl. XxxIv, 
figs. 1-4, 6-15. 
1884. Orthis testudinaria WALCoTYT. Monograph of the U. S. Geological Survey, vol. viii, p. 72, 
pl. x1, fig. 10. 
1892. Dalmanella testudinaria HALL. Paleontology of New York, vol. viii, pt. i, pp. 190, 206, 
pl. vB, figs. 27, 39. 
1892. Orthis rogata SARDESON. Bulletin of the Minnesota Academy of Natural Sciences, vol. iii, 
: p. 331, pl. v, figs. 1-4. 
For other synonymy see Davidson’s Monograph of British Silurian Brachiopoda, p. 226. 
