Figs 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
bo 
and 3. 
4 and 5. 
6 to 9. 
6 and 7. 
8 and 9. 
- 10 to 14. 
10 to 12. 
13 and 14, 
15 and 16. 
17 to 21 
Ate 
18. 
19 and 20. 
21. 
. 22 and ? 23. 
22. 
23. 
29) tor sl: 
29 and 20. 
32 and 33. 
34 to 41. 
36. 
37. 
38. 
39 and 40. 
41. 
27 and 28. 
PLATE XLI. 
PAGE. 
WiHITELUGA UU GAMENA TSI). sle,staye tess oratars att bake «rose deteie sto eaiars) ctotaletomietnlonsrsvalereeyainre e arotoe 569 
Left side of a cast of the interior. Middle third of the Trenton shales, Minne- 
apolis, Minnesota. 
WHILELDTA, CONCENTRIGA WiIrichix,,. 5 tetci- cos celslomteasirusaie cle sinicls aieietomiersta ioe emer: 569 
The right side and a front view of the type. Middle third of the Trenton shales, 
Minneapolis, Minnesota. 
WHITELULACMEGAMBONA! WihIGHeld, (Speiee-ctece sors s/teciele eicy-tete 5 s)o.07s arsieibyoleie reine eer. 
Two views, lateral and anterior, of a good cast of the interior. Trenton lime- 
stone, Minneapolis, Minnesota. 
WiHITHEIVAS COMPRESS AM OMET CH cH u's scrativs strettes operate iearelaene reticle ei centers 
The right side and a front view of an internal cast, differing slightly from the 
type of the species. 
Two views, side and dorsal, of the original type of the species. Middle third of 
the Trenton shales, Minneapolis, Minnesota. < 
SWVC ESTE ACS ERIN CAT Ate UD ITSH C Hier sts scstevsjsyzinvctarcietes eave rats laveteisy «/ejcle ae ietatersTisieyisielerereicie stelctersss 
Dorsal, side and front views of an average specimen. 
The right side and a posterior view of the largest cast of the interior seen. 
Galena shales, Goodhue county, Minnesota. 
AVERITT AQSP RAs COLE UAUMU LCI japaiepreererstaran-tefeccielslotenty tasiaibisTersieeisienctsteriate HomeeadupuoCAnd 
The left side and a dorsal view of a large and well preserved cast of the interior. 
Galena shales, Goodhue county, Minnesota. 
WHEREAS SCORTE TDL SU) Clg ais. ctersvayeyeake rs ietvoaturanteketey sieiclelelctcrey-siete’sereeretelstatstnl ener tlerete 
A very large left valve from the middle third of the Trenton shales at St. Paul, 
Minnesota. 
Hinge of same. The cardinal teeth are abnormally developed. 
Anterior and side views of the original type of the species. Middle third of the 
Trenton shales, Goodhue county, Minnesota. 
Hinge of same x 2, showing the cardinal teeth, the striated escutcheon and the 
posterior internal ligament supports in a very satisfactory manner. 
Win TRA SUB CAVRITINGAUIA coTN-c SI) >. nfetalevesetalere store cele tetensrererctoteletel iarsteler esatal cine ciarelatefetereiate tay 
A well preserved internal cast of aright valve. Middle Galena, Wykoff. Minnesota. 
Cast of a left valve, supposed to represent an earlier variety of this species. 
Lower Trenton limestone, Jo Daviess county, [llinois. 
WHT PE TIAUCVON TR IC OSA EVA LIS 1 cpay.tecrcrevreretaterelnotatarototetereterstaqere wie wistareleetctercraierciaiare shansters 
Tnternal cast of a right valve in which the anterior margin is uniformly rounded. 
Anterior view of same, with the left valve restored from another specimen. 
Outline of the antero-dorsal part of a left valve in which the anterior margin is 
sharply rounded above. Trenton limestone, Watertown, New York. 
WHITELLA STERLINGENSIS Meek and Worthen ...............00seseeee sees sence 
Antero-cardinal and lateral views of the original type of this species. The speci- 
men is a cast of the exterior. Upper part of the Hudson River group, Sterling, 
Tllinois. Illinois State Museum. 
SABEORDIA= MODEST Ate WIL ClaWetetsarscrotcin tara olarersisvalece otavens clave stsyetayofe are: etelotatisierctexeralcraratatereieet ie 
The left side and a front view of an entire cast of the interior, natural size. 
The specimen is of the average size. Galena shales, Goodhue county, Minnesota. 
The left side of same.x 2. 
DAMKORDUAT SULCODORSATAY (WGC stereo steers iareuei<cteieralcleleisielo/o|ata)elsletsleaeete! oltehslstaistereteletareuet= 
Antero-cardinal and lateral views of the specimen described, Upper part of the 
Hudson River group, near Spring Valley, Minnesota. 
SAERORDIAT VENDRVATIIS MI Sp erstveccss we vclozereleveieieyheperetsveterstarchevalabetot oleressiela wiaereheretetana cyevete Meters 
Cast of the interior of a left valve. Spring Valley, Minnesota. 
Gutta-percha impression of a natural mold of a small left valve in the base of a 
bryozoan. Hudson River group, Iron Ridge, Wisconsin. 
Anterior view of same. 
Hinge of a right valve. 
A left valve. 
Anterior and cardinal views of same, with the right valve restored from the 
original of figure 387. : 
Hinge of the left valve. Upper beds of the Hudson River group, near Spring 
Valley, Minnesota, 
570 
568 
572 
574 
S71 
572 
573 
567 
626 
