Figs. 59 and 60. 
59. 
60. 
Figs. 61 to 64. 
. 61. 
62. 
63 and 64. 
Figs. 65 and 66. 
Figs. 67 to 73. 
67 and 68. 
69. 
70 to 72. 
73. 
Figs. 74 and 75. 
74. 
75. 
Figs. 76 to 82. 
76 to 78. 
79. 
80. 
81 and 82. 
Figs. 83 to 87. 
83 and 84. 
85 to 87. 
Figs. 88 to 90. 
88 and 89. 
90. 
Figs 91 and 92, 
Figs. 93 and 94, 
Figs. 95 to 97, 
PLATE XLII.—Continued. 
PAGE. 
OTENODONTA, SOCEATIS Met SD iiss cnc .ccicisicieiey nine v'sle (eis aisiaicie's\neininis «\sjalelaiaia Seba nSdoncoeeeaubsodenechmercisaac su agsoeor 594 
Outline views of three specimens of different sizes and showing slight variations in form, 
Hinge of two right valves, x 3, showing slight differences in the anterior parts. 
CTENODQNTA CALVINI, n. Sp.. Sicess/ ental 4 weie is steeineta elon ats 596 
An excellent cast of the interior of a left wae showing. sanecular scars sand rayeon more plainly “ine 
usual. In this specimen the length aiso is a little greater than in the others. 
Another cast of a left valve. Minn. Geol. Sur. Mus. Reg. No. 8628. 
Lateral and cardinal views of a cast of a right valve, representing the usual characters of the species. 
CTENODONTA MADISONENSIS, nl. Sp 
The left side and an anterior view of a testiferous example of this species. 
OTENODONTACHE OUND AGE All masareajnreinictatal=isisiiels sal aie o claleteinm hase sleintelt el \lelsieloieeielalee vie sialic he seelssaitioctcnlest: eiscisie sistent : 
The right side and an anterior view of a cast of the interior. In many specimens the posterior 
margin is more rounded 
A small part of the external surface magnified to show the fine concentric and radiating lines. 
Cardinal and anterior views and the right side of a specimen preserving the shell. 
The wavy hinge line as shown on a Cast of the interior, x 5. 
CTENODONTA SIMULATRIX, n. Sp . Socciks * Soc oon 5 5 saodLo 
A cast of the interior of a right males Bromine ine ehanenian sears 5 andi ‘retaining a little of the shell 
about the beak. 
As much of the hinge as can be made out from the preceding specimen. 
CTENODONTA ALBERTINA, TD. SP.......0---.e2 eee aise a tale clstoeicietatetolatcialeletia cals ota ciepeere sintete picts onan atetsiets incetensralalststal dosabecs 
Three views of a large specimen having the posterior end a little narrower than usual. 
A smaller specimen of the usual form. 
Hinge of a large and smaller right valve, showing the subrostral pit and the geniculated teeth. 
Cardinal and lateral views of a cast of the interior which retains a part of the hinge, 
OTENODONTA OBLIQUA Hall. ..... ... Aran erin seco nase,taatacpen Sy aee ase o5 SO ABR OSE taaon oe ne acD OSS ub cacoad 
Lateral and cardinal views of a small specimen of the large northwestern variety of this species, x 5. 
As usual, the specimen is a cast of the interior and shows the muscular scars and impressions of the 
hinge denticles very clearly. 
Three internal casts of a small form of the species from the Cincinnati group of Ohio, x 5. 
CTENODONTA COMPRESSA Ulrich ............+-- Scab bodicnoscceos Pekaricetie cieraeler Tes iotastainclole'stcinate’< thale'a ciniale leis) ctsiasieteete 
(See also plate xxxvil, fig. 29.) 
Posterior and lateral views of a left valve. 
The greater part of the hinge of another left valve, X 5, showing the various parts in a beautiful 
state of preservation. 
OTENODONTA HAMBURGENSIS Walcott ..........02 cece cece cece cee e eee Gd sAnabosseage os 
A right(?) valve of the natural size and X 5. 
CTENODONTA ALTA Hall. mopeidoscnsos 
Lateral and posterior views Sor a east of the interior: 
OTENODONTA INTHRMEDIA) UIriGh >.< ccjs.ccteers = soninecle aleelsinc es cles nies siasceenan coc aakon aa 
95 and 96. Lateral and posterior views of a right valve preserving much of the shell. The opposite valve is 
restored in the profile view. 
97. A sharply marked cast of the interior of a left valve. In this specimen the posterior extremity is 
unusually produced, | 
Figs. 98 to 101. OTENODONTA RECURVA Ulrich........... Semaidalaa ante mtearieieeioalas eileniesaieiesnisinanics Ca rocde cco ShbossoossGude 
98 to 100. Posterior, lateral and cardinal views of a 3 pertect specimen of this species: showing the usual form, 
the anterior sulcus and the sharply defined anterior and posterior lunettes. 
101. The greater part of a hinge of a left valve, X 2, showing the arrangement of the denticles, the 
sharply elevated outer margin and the ligamental area on the right side of the beak. 
Figs. 102 to 106. CTENODONTA SIMILIS Ulrich.......... Secon: stecodLsacosas Se shasecg  -danodeega Sanide 
102. Hinge of a left valve of this Bpecies: x 2, ishowivg the puinicipal features upon which this species is 
separated from C. recurva. (See fig. 101.) 
103. The left side of a specimen, showing the usual form of the species. Minn. Geol. Sur. Mus. Reg. 
No. 8368. 
104 to 106. Lateral, cardinal and posterior views of a specimen having an outline very similar to that of 
CO. recurva. But the absence of the anterior sulcus, the greater convexity of its valves and the 
less sharply defined lunettes are all characteristic of C. similis and prove its distinctness from 
C. recurva, 
597 
595 
604 
605 
601 
