Figs. 48 to 52. 
48 and 49. 
50. 
51 and 52. 
Figs. 53 to 56. 
53. 
54. 
55 and 56. 
Figs. 57 to 59. 
Figs. 60 to 61. 
Figs. 62 to 65. 
62 to 64. 
65. 
Fig. 66. 
Figs. 67 and 68. 
Figs. 
Figs. 
Figs. 
Figs. 
Figs. 
69 to 72. 
69 to 71. 
72. 
73 and 74. 
75 to 77. 
78 to 81. 
82 and 83. 
. 84 to 88. 
84. 
85 to 87. 
88. 
89. 
PLATE XLIII.— Continued. 
PRIMITIEL LA CONSTRICPA (Ne IGEN CUISP = sont stonsleralevolaiatetorstetolat ota tafe state rata tole lo\oiete ra piateleyars 
Three views of a right valve; from the base of the Birdseye limestone at High 
Bridge, Kentucky. In this form the anterior end is rounded and the border 
scarcely developed. 
Two views of aright valve, representing the prevailing form of the species in 
Minnesota. 
Lateral and dorsal views of a longer right valve, from the lower third of the 
Trenton shales at Minneapolis, on which a small raised spot, situated just 
behind the center of the valve, is barely distinguishable. 
IPRIMITIR EGA SRIMBATAS SS! a lserverer es eraterabs hein eretee ones lerereietatclle Mere eievelo) Ste) ofoksls ofeterete’sfaletats 
Interior of a right valve. 
Anterior and lateral views of another right valve. 
Lateral and dorsal views of a left valve. Lower third of the Trenton shales, 
Minneapolis, Minn, 
PRIMPTIA . GIBBERAS DAS pe ih sete Fee Sie RIK oe eralel ea ten ealecore ehaioisiciciale eieje wisi oietety 
Three views of a left valve. Hudson River shales, near Spring Valley, Minnesota. 
ERIMETLAS DM PLC VATWA TAS Dieteters nis oh etalea iol eveeeiels eres nie atelaiete iin sieietsieteicteteieleis ies seers 
Lateral and ventral views of a left valve. Middle third of the Trenton shales, 
Minneapolis, Minn. 
PRIMERA SUC GD UA eS Dis evel oc latelet aise Tele . DESY SBD Do DUP a aooteeb ona oaone co 6255 
Three views of the exterior of a left valve, obtained by an impression in gutta 
percha from a natural mold. Hudson River shales, near Spring Valley, Minn. 
Cast of the interior of another left valve, from the same locality. 
IP RIMLOLAS UPHAM. MUS Dire eeet rea te cee rien tesistciie eteielels iawn elaine eisieteiattevehereteletc stars 
Three views of aright valve. Galena shales, Cannon Falls, Minnesota. 
[PRIMUTTANCHIGAD AgeIQy SD. te aisleyorete:¢sefe levels = ctoteraitreie’ is RMT eft eee ae Peele at otal lsteielminis ee iteter 
The exterior and a ventral view of aright valve. Middle third of the Trenton 
shales, Minneapolis, Minn. 
SPRL VAS MC AG TD a SPosis rds tncicicva dete els ju talarel ave tatebetadefens [o¥e tlt letont Be fetiafete bal fetcter<[alur-Velote]=tm\biels 
Three views of aright valve. Galena shales, near Cannon Falls, Minnesota. 
Interior of a left valve, from the same locality, supposed to belong to this species. 
The outline is somewhat different from the preceding, but there is reason to 
believe that the valve is imperfect at the antero-ventral margin. 
IPRIMTTTAY SANOTT SPAUIEL, Ge Siar w afesoriieters ears ederere cer eerie ia ee emer toleiterakare/ eho 
Two views of a right valve. Upper third of the Trenton shales, St. Paul, Minn. 
PRIMED TA “UNECORINES WUTICH ss ce cieictet eyesore ereiepejepelo eter velelsleleraivin'© ofalslalalsietelol=lalai=]=1alslmie/e 
Three views of a right valve, from the lower or Utica horizon of the Cincinnati 
group at Covington, Kentucky. The specimen is one of the original types of 
the species. 
IPREMITEA, MAMUMPAUIAS ILS: « «1 akceiteici me eivisterstette sie ror tatate stat@rats Marre otelo.0)c(ateinioieleletnlsiriateratersts 
Dorsal, lateral and ventral views of aright valve. Lower third of the Trenton 
shales, Minneapolis, Minn. 
IBEYRIGHIA™ ENUTUATIS, I-tS Db sere aie ckiaisreveic's slesetlcleteuers ala aloha) ole) ais intaseyela ieOv elrfaUslelelas=!otelslieyaiai= 
Lateral and ventral views of a left valve. Middle third of the Trenton shales, 
Minneapolis. 7 
MOOREA PUNCTADA QU SPs terescie sacle s © clalvinsoleys lore alc ievele!arnistctintels slic le’efsjeisialelnialimsisiniia) (a) stones 
A right valve. 
Three views of a left valve. 
Another left valve in which the marginal ridge is twice interrupted along the 
ventral border. Upper third of the Trenton shales, St. Paul, Minnesota. 
MOOREA. ANGOUUTARIS/IN. [Sp aU PAGE RR AIEEE ME eto cbtae teeta iste borate Be) nisin, «5 2.0 
(See also plate XLVI, figs. 15 and 16.) 
Side and ventral views of aright valve. Middle third of the Trenton shales, 
Minneapolis, Minn. 
648 
655 
653 
