PE Aaa XSW). 
PRODUCTLUS) SHUMARDIANUS 2s see eos soe meee serie seen enioetessselesaio Sesnosctoc]e SEO SO EEOC 
Fig. 1. View of the dorsal valve. Natural size. 
PRODUCTUS TRUNCATUS .-.. 1.2200 <2 <5 en 00 n= oon 2 cn ne veces een enn ne nn nnn nnn eee e an an ane 
Fig. 2. View to show the truncated apex of the ventral valve. Natural size. 
REYNCHONMDLA) HORSKORDIq.2-)o. === se ae = m= amet = nie om eels etal mele ee ete lee elena 
Fig. 3. Ventral view of an average size specimen. See plate xv, fig. 6. 
ATR Y PASDEBQUAMATA sno. son jeans meee ean nis eee tesee m= steemisians esteem rie eier see ieaieatata te 
Fig. 4. View of the ventral valve. 
4a. Cardinal view to show the small area. Natural size. 
EREGNON OH ONT AG (Lin) STINT ACOA Ole re eee ete etl li 
Fig. 5. Dorsal view of a characteristic specimen. Natural size. 
ATRYPA RETICULARIS. .--.--.----- - 22-2 + cee oo - oo one ce ne ee ne cen nn enn enn s ewe e en nn cone 
Figs. 6,6a,6), Ventral, lateral, and dorsal yiews of the small variety mentioned in the text 
as characteristic of the Niagara formation. 
| Mir an(GlttOscI FIL eeIDLOLC UIs! oop een bc oE eb babe SCOSS SeQdo Sodas cad Guise Sencocn SSS SSECES Seas ocr 
Figs. 7,7a. Lateral and ventral views of an average size specimen. 
Midian (leti gr nio.w ISO MUN Co 6eds ooSsc no secco cobescisesoas odsace Decors caSsssCnceso saps ooTer : 
Fig. 8. Dorsal view vf a very striking example of the species, 
EPELVON CO NESTE AW (1) NERS ASU NS ISS uote ee ee 
Figs. 9,9 a,9b. Ventral, lateral, and dorsal views of the ordinary type of the species. 
SSD UENE RA Pe ARR A es sn ee rt 
Fig. 10. Ventral view of the only specimen obtained, showing the coste and fine radiating 
striz. 
Stauano ony (( C) aie nur ally Se one Senos cen ses SODeBeSScDOS0b RODSbS cde Sonccece Code SS cb cose Beas 
Figs. 11, 11a, b. Dorsal, lateral, and ventral views of a specimen from which most of the 
outer surface is removed. , 
13). Ventral valve with a portion broken away, showing the cast of the muscular 
impression. 
13c. Ventral valve of a broad variety of the species, showing the area and small del- 
tidium in place. See plate iii, figs. 3, 3a, b, 6, 6a. 
SPIRIMERA(M.) RARECOST Are cee = nae tain Heme ome tele ees Sisweewalea ed aa'sicleS oem alaitars 
Fig. 12. View of the partial cast of the dorsal valve of a small shell. See plate iv, figs. 2, 2a. 
SPIRIFERA (M.) MAIA -.-....--..--------- BEE Hic es oe oC ene do caaoec oe a tha ooes HasSt concede 
Figs. 13, 13a. Dorsal and lateral views of an average specimen of the species. See plate 
iii, figs. 1, 1 a-e. 
SPIRIFERA (M.) GLABRA, var. NEVADENGIS «<22-0 c- ooo sso nc ca eelene=(= oon see sane ele eles =e 
Figs. 14, 14a, b. Dorsal, lateral, and front views of the largest and most transverse speci- 
men in the collection. See plate iii, fig. 5. 
PEN TAMER US (M.)) COMIS Seo lecinee inna) eae Sete ate ee ee a 
Figs. 15, 5a, b. Dorsal, lateral, and ventral views of a transverse, smooth specimen. See 
plate iii, figs. 4, 7, and plate xv, figs. 5, 5a, ¢. 
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