Fig. 
Fgs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
15 to 
15 and 
18 and 
20 and 2 
22 to 
25 to 
28 to 
29 and 
31 and 
33 and 
35 and 
37 and 
10. 
11. 
19. 
24. 
27, 
30. 
28. 
30. 
32. 
31. 
32. 
34. 
36. 
38. 
PLATE XL. 
CYRTODONTAMOVAIROR MIS SUNT CH Aa ser-tonrerwiahe’s «cra eta crelelarare’s coneeey eee natetets tatete eit eta oraterecehe 
(See also plate xxx1x, flg. 46.) 
Anterior view of the type. 
GYR TODON TWAS BIGEENG Sy, hsi8 Dylerclacutaisietsforciote arate inlore elesate\e eaeiaeto/ oe ietel eset asetoke ere) eee 
Cast of a right valve from the lower Trenton limestone at Cannon Falls, 
Minnesota. 
Three views of the best specimen seen. Lower Trenton limestone, Dunleith, 
Tllinois. oe 
Another specimen from the preceding locality. 
CXYRTODON TA: CINGUGAT AS UMELCH 5s aleicleix cis creat inivic aveie ane icielenele eaters see peromicisiciae ee carte 
Anterior view and the right side of the original type. Middle third of the 
Trenton shales, Minneapolis, Minnesota. 
CYRTODONTA GRANDIS Ulrich, and varieties...................2. seeee sietiyecaiemectete 
(See also figure 43, a-k, p. 547.) 
Cast of a large right valve of the var. germana Ulrich. Galena shales, Goodhue 
county, Minnesota. 
Cast of a small specimen from the middle Galena at Lime City, Minnesota. 
This specimen agrees better with the var. germana than with the typical 
form of the species. Geol. Sur. Mus. Reg. No, 4102. 
A small specimen (cast of a right valve) of the typical form. Middle Galena 
Wykoff, Minnesota. 
Interior of the original type of Cypricardites germanus Ulrich. Upper Trenton 
near Danville, Kentucky. 
Part of the interior of the var. luculentus Sardeson, as shown in a gutta-percha 
impression from a cast of the interior belonging to the Survey collection. 
A good cast of another right valve of the same variety and from the same 
locality. Upper beds of the Hudson River group, Granger, Minnesota, Geol. 
Sur. Mus. Reg. No. 8332. 
ORV LODONWAGIDENN ESE Aer llitel Cintas etatel islet ctraeeeWelaseye¥elodeseietete ees icaatstetsielters te crete eneiete iets 
Lateral and anterior views of a large right valve. 
Hinge of same. The cardinal teeth are obscure in the specimen and may not be 
exactly as drawn. 
Anterior and lateral views of another right valve, differing from the preceding 
in being more uniformly convex. Upper part of the middle third of the 
Trenton shales, Goodhue county, Minnesota. 
WSS hop-qonigd. wa 0. on py USP SENTING Pe oon oo dees rpcopnodonecndomeccn HeBEOoO. HonoodeD 
(See also plate XXXvVIII, fig. ns and text p. 479, fig, 36—Iv.) 
Imperfect interiors of two right valves, showing slight differences in the cardinal 
teeth. Upper Trenton, near Danville, Kentucky. 
PADI S(O UA DION Lop TONG UW AVAN AO a pooduGssnasis nadodedooonAcodagahccushaeenoosans 
Three views of the type specimen. Upper part of the middle third of the 
Trenton shales, Goodhue county, Minnesota. 
IPENTHOCAR DEA SB ER EC TAcm Will CI. ves raters) slesclarsrereisraleterstenalelarctcteretelatlefeatehefeas liad sts tele tere reteye 
Three views of the typespecimen. Galena shales, Goodhue county, Minnesota. 
WHITELLA QUADRANGULARIS Whitfield, sp ..........-. 2 ++ se eeee eect eeee eee ee ee 
An imperfect specimen doubtfully referred to this species. Hudson River group, 
Spring Valley, Minnesota. 
Dae and antero-cardinal views of a cast of the interior from Savannah, 
1n01s, 
WHERE A, OBLIQUADA UWI Chi sears, c. stereo felotecvne o cleiateioe cisreteversieactetetanslersieselaner teks atenaiieters 
A cast of a left valve from the upper beds of the Cincinnati group, near Blan- 
chester, Ohio. 
The interior of a left valve, showing the hinge with its cardinal teeth, escutcheon 
and posterior internal ligament supports, and faint muscular impressions. 
The outline is imperfect posteriorly, causing the shell to appear less oblique 
than it should be. Hudson River group, Spring Valley, Minnesota. 
TRACHNOPHORUS SUB A CUMS a UML CI yeje15 oicietyesyetereneteleraieteneiateterchepata sDaterale <telapeteteletete tite tetate 
Cast of the interior of the natural size and twice magnified. Trenton limestone, 
Minneapolis, Minnesota. Geol. Sur. Mus. Reg. No. 8338. 
THCHNOPHORUS MILISTR LAD US WUTC My aaleteia cc clee cre svaictalousiciele isle siolstessia iebele clareefaleleislere iets 
Left valve of the natural size and a small portion of the surface enlarged to 
show the regular character of the fine concentric lines. Upper part of the 
middle third of the Trenton shales, Goodhue county, Minnesota. 
TPECHNOPHORUSDIVARICAT US) UW lrl Chircicjorescateiasctotetels) tateve ele palelelereieve ol te teielelahetate le elatelsyaie) ala 
The type specimen, a perfect left valve, of the natural size and enlarged two and 
one-half times. Upper third of the Trenton shales, near Cannon Falls, Minnesota, 
545 
547 
546 
557 
576 
577 
566 
565 
614 
615 
616 
