PLATP] III. 



>.-f,-ollll 



I--,-. 



Fijr. 



Fiff. 

 Fig-. 



I. Laterals. 



c. Centrals. 



8C. Subnardinals oi' iiostmedians. 

 <T. Crescent. 



e. Extei-nals. 



X. Composite jiosterioi-s. 

 P. Pedicle-groove. 

 F Foramen. 



I'. Kdiaminal jiits. 



s. Septum (median), 

 s'. Septum (lateral), 

 o. Vasculai- trunks (oviducts '!)■ 

 d'. Subapical area, 

 cb. Cardinal bosses, 

 fc. Foraminal callosity. 



LKPTOBOLUS, IIaf^l. 



I'age 78. 



Lei>tobolus insignis, Hall. 



.1. An internal cast of a ix-ilicle-valve ; Bhowing the long, curved lateral scais and a faint indication 



of the posterior muscular depression. X 10. 

 2. An internal cast of the brachial valve, .similaily enlarged, and sh(i\ving the median septum and 

 two lateral grooves, which correspond eithi'r to the seal's (z) seen in fig. 0. or to the latei'al septa 

 (s') in fig. 10. 



Utica slate. Holland Patmit, iV. 1'. 

 I{. The exterior of the shell ; showing the concentric and radiating striae. X 8. 

 Utica slate. JUiddleville, N. ¥. 



4. The inlerioi- of a pedicle valve ; showing the lardinal area and groove, and the thick, calloused 



fulci-a of the lateral muscles. X li). 



5. Another interior of this valve, in which the transverse extensions of the lateral fulcra are continu- 



ous. The jiosliuior depiesseil area beais the impresi-ion of the centi-al muscles, and indicaticns 

 of a subdivi-sion of the ])itted suiface into differentiated scars. X 15. 

 B. The inteiioi- of a brachial valve ; showing the grooved area, conspicuous median septum and faint 

 lateial scai's. 



Hudson Rivei- group (Utica horizon). Covington, Kentucky. 



LePTOBOLU.S OCCIDENTAI.IS, Hall. 



7. The exterioi- of the .shell. X 8. 



Dark .-ihale of the Utica horizon. Hawley's Mill, 12 miles iiort/i-west of Dulruque, lovxL. 



Leptobolus lepis, Ilall. 



8. The interior of a iiediclo-valve ; showing the cardinal groove and the divei'ging .septa. X 12. 



0. A cast of the interior of the pedicle-valve ; showing the central scai' anil the transvei-se extension 



of the laterals. X 12. 

 10. The interior of the brachial valve ; showing the grooved cardinal area ami the median and lateral 

 septa, each of which is bifurcate at its extremity. X 12. 

 Hudson River group. lAcking River, Ohio. 



SCHIZ0B0LU8, Ulrich. 



Page S7. 

 SCHIZOBOLU8 TRDNCATUS, Hall (sp.). 

 Fig. II. The exterior of a pedicle-valve. X 3. 



Genesee slate. We.tley-n New York. 

 Fig. 12. The interior of a pedicle-valve, drawn from one of Mr. Ulkecmi's original specimens ; showing the 

 pedicle-slit, the cominisite muscular s(^ars abutting against the median sejitum, and the long, 

 cuivea lateial scai-s. X 5- 



Black slate (Genesee). Madison county, Kentucky. 

 Fig. 13. The exterior of the brachial valve. X 3. 



Genesee slate. Western New Yink. 

 Fig. H The inleiior of the brachial valve ; showing the septum an<l faintly defined nuiscidar impressions. 



X o. 



Black slate (Genesee). Madison nounty, Kentucky. 



