PLATE LVIII 



PAGE 



Fig. 1. ORTHODESMA NASUTUM Conrad 289 



A fairly well preserved right valve showing the narrow, extended, 

 nasute form. 



Ordovician (Cincinnatian), Orthorhynchula bed at top of 

 Fairview formation, Tuscarora Mountain, one and one-half 

 miles southeast of McConnellsburg, Pennsylvania. 



Figs. 2, 3. ISCHYBODONTA UNioNoiDES (Meek) 281 



2. Right valve of an example presenting the test. 



3. Impressions of inner side of a right valve showing the anterior 



muscular scar. 



Ordovician (Cincinnatian), top of Fairview or base of 

 McMillan formation, Covington, Kentucky. 



Fig. 4. RAFINESQUINA SQUAMULA (James) 264 



Impression of the shell in sandstone. 



Ordovician (Cincinnatian), Orthorhynchula bed at top of 

 Fairview formation, Tuscarora Mountain, one and one-half 

 miles southeast of McConnellsburg, Pennsylvania. 



Figs. 5, 6. ORTHOCEBAS LAMELLOSUM Hall 324 



5. View showing separation of septa and other characters of the shell. 



6. View illustrating position of the siphuncle. 



Ordovician (Cincinnatian), Pulaski shales near Pulaski, 

 New York. 



Figs. 7-9. LIOSPIBA MICULA (Hall) 296 



Top, bottom, and side views of a nearly perfect example. 



Ordovician (Cincinnatian), Eden shale, Covington, Kentucky. 



Figs. 10, 11. ISOTELUS MEGISTOS Locke 343 



10. Meek's type of Asaphus megistos Locke (Pal. Ohio, Vol. 1, pi. 14, 



fig. 13) enlarged one-third, representing the spinous form 

 (? male). 



Ordovician (Cincinnatian), near top of Fairview formation, 

 Cincinnati, Ohio. 



11. Hypostoma of a larger example. 



Ordovician (Cincinnatian), lower part of McMillan forma- 

 tion, Morrow, Ohio. 



Fig. 12. MODIOLOPSIS MODIOLARIS (Conrad) 286 



One of Hall's original figures which well represents the usual aspect 

 of the species. It illustrates a slightly compressed right valve. 

 Ordovician (Cincinnatian), Pulaski shales near Pulaski, 

 New York. 



Figs. 2, 3, 7-9 are after Ulrich and 5, 6, 12 after Hall. 



408 



