BRACHIOPODA. 459 
Rhynchotrema ainsliei. ] 
Ruyncnotrema arnsurer N. H. Winchell. 
PLATE XXXIV, FIGS. 1—8. 
1886. Rhynchonella ainsliei N. H. WINCHELL. Fourteenth Annual Report of the Geological and 
Natural History Survey of Minnesota, p. 315, pl. , figs. 5, 6. 
This species has the essential characters of R. inequivalvis, therefore a detailed 
description will not be necessary. It differs from the latter in being usually larger, 
more transverse, and in having from twenty-eight to thirty-four plications, with six 
to eight on the fold, and five to seven on the sinus, while R. inequivalvis has from 
sixteen to twenty-two plications, with four to five on the fold. Compared with 
Rhynchonella altilis Hall* of the Chazy group of New York, Rhynchotrema ainslier 
is seen to be more transverse, has a more prominent fold and sinus, is less globose, 
and on the average has a few more plications. 
Formation and locality.—Restricted to the lower portion of the Trenton shales, where it is common 
at Minneapolis, Cannon Falls, Lanesboro, Fountain, Chatfield and Preston, Minnesota; Decorah and 
McGregor, Iowa. 
Collectors.—C. N. Ainslie, C. L. Herrick, W. H. Scofield, J. C. Kassube and the writers. 
Mus. Reg. Nos. 324, 326, 734, 4031, 4938, 4974, 5480, 5489, 5492, 5498, 5505, 5512, 5517, 5521, 7917, 
“8204-8207. 
RHYNCHOTREMA INZQUIVALVIS Castelnau. 
PLATE XXXIV, FIGS. 9—25. 
(843. Spiriferincequivalvis CASTELNAU. Essaisur le Syst?me Silurien de l’Amérique Septentrionale, 
p. 40, pl. xrv, fig. 8. 
1847. Atrypa increbescens (partim) HALL. Paleontology of New York, vol. i, pp. 146, 289, pl. xxxu1, 
figs. 13a-13h; ? pl. LX XIX. fig. 6. 
1856. Rhynchonella increbescens (partim) Burnes. Canadian Naturalist and Geologist, vol. i, 
p. 207, figs.. 11-14. . 
1863. Rhynchonella increbescens BILLINGS. Geology of Canada, p. 18, fig. 153. 
1875. Trematospira (?) quadriplicata Mi~tLER. Cincinnati Quarterly Journal of Science, vol. ii, 
p. 60, figs. 6, 7. 
1889. Rhynchotreta quadriplicata MILLER. North American Geology and Paleontology, p. 370. 
1889. Rhynchonella increbescens NETTELROTH. Kentucky Fossil Shells, p. 83, pl. XXxXrv, figs. 26-29. 
1892. Rhynchonella minnesotensis SARDESON. Bulletin of the Minnesota Academy of Natural 
Sciences, vol. iii, p. 333, pl. rv, figs. 21-23. 
Compare Atrypa subtrigonalis HALL. Paleontology of New York, vol. i, p. 145, pl. xxXII, 
figs. 12a-12c, 1847. 
The original description of R. increbescens was drawn up from specimens now 
referred to that species and to R. capax Conrad. That by Castelnau is not accessible 
at the present time. The following description is based on material derived from 
Minnesota, Kentucky and New York: Shell small, varying from narrow to broadly 
subtriangular in outline, smooth in the nepionic stage, depressed-convex during the 
nealogic period, and becoming more globose in ephebolic and geratologic growth; 
posterior lateral margins straight or somewhat convex, rounding rapidly into the 
sinuous anterior edge. Surface with prominent subangular plications, from sixteen 
to twenty-two on each valve, with from three to five on the fold, and two to four in 
*Pal. N. Y., vol. i, p. 323, pl. 1vbis, figs. 91-9d. 
