PLATE XXIX. 
I'AOK. 
Figs. 1 to 4. LiNouLA ELDEHi Whitfield 3.TJ 
1. Dorsal viow of an cxfoliatod spocimen to sliow th<; flattening along th<; lati;ral 
luargins. Trenton lirnostone, Minneapolis, Minn. Minnesota Geological Sur- 
vey collection. 
2. Interior of tine ventral valve, drawn from a natural cast, the usual mode of 
occurrence of this species, y, unibonal scar; /t, centra) scars; A;, middle laterals; 
ji, anterior lateral and transmedian scars; v, vascular sinuses; vh, vascular 
trunks. (After Whitfl.'ld.) 
3. View of the interior of the dorsal valve taken from a natural cast, j, anterior 
lateral scars; lik, lateral, transmedian and middle lateral scars; other l<;tters 
as above. (After Whitfield.) 
4. Profile outline, to show the relative convexity of valves and the great elevation 
of the ventral beak. Trenton limestone, Fountain, Minn. Collection of C. 
Schuchert. 
Figs. 5 and 6. Lingula eva Billings 341 
5. A dorsal valve with strong radiating lines in the anterior half. 
6. Profile outline of the same specimen. Trenton shales, Fremont, Winona county, 
Minn. Minnesota Geological Survey collection. 
Figs. 7 and 8. Lingula pnrLOMELA Billings 342 
A view of one side of the only specimen seen and a profile outline of the same. 
Base of Hudson River group, near Granger, Minnesota. Minnesota Geological 
Survey collection. 
Fig. 9. Lingula uiciniformis Hall 343 
Ventral valve, showing the rounded Obolella stage of growth in the posterior 
portion. Trenton shales, St. Paul, Minn. University of Minnesota collection. 
Figs. 10 and 11. Lingula riciniformis, var. galenensis W. and S 344 
View of the ventral valve and profile outline of the same. Galena shales, near 
Kenyon, Minn. Collection of W. H. Scofleld. 
Fig. 12. Lingula cobouugensis Billings (?) 346 
View of a specimen provisionally referred to this species. Trenton limestone, 
Chatfleld, Minn. Minnesota Geological Survey collection. 
Figs. 13 and 14. Lingula (Glossina) hurlbuti N. H. Winchell 347 
13. A view of the ventral (V) valve of the type specimen. 
14. Enlarged view of the concentric surface stria?, x 2*. Middle Galena, Mantorville, 
Minn. Minnesota Geological Survey collection. 
Figs. 15 to 18. Lingula (Glossina) deflecta W. and S 348 
15 and 16. A dorsal valve and profile outline of the same. Galena shales, near Fountain, 
Minn. 
17 . Natural cast of the interior of the dorsal valve, showing the striated internal 
cardinal area, the vascular trunks and sinuses which apparently surround the 
anterior and lateral muscular scars. 
18. Natural cast of the ventral valve of the same specimen, preserving the markings 
of the muscles and vascular system. Hudson River group, Spring Valley, Minn. 
Collection of C. Schuchert. 
Figs. 19 to 22. Lingula lOWENSis Owen 349 
19. A dorsal valve with the shell broken along the median line, which is due in great 
part to the decomposition of the shell forming the internal septum. The pro- 
jecting cardinal area of the ventral valve is also shown. 
20. Profile outline of the same specimen. Galena limestone, near Hader, Minn. 
Collection of W. H. Scofleld. 
21. An internal view of the dorsal valve, taken from a gutta percha impression. 
/;., central scars: s, septum; x, concentric laterals. (After Hall.) 
22. Natural cast of the ventral valve of the specimen from which figure 21 was taken, 
showing the slightly elevated muscular scars and median septum. Galena 
limestone, near Fountain, Minn. Collection of C. Schuchert. 
Figs. 23 and 24. Siphonotreta (?) minnesotensis Hall 358 
23. View from the dorsal side of a specimen retaining the valves in juxtaposition 
and preserving most of the epidermal layer of the shell. 
24. The ventral valve of the same specimen, imperfect in the umlumal region, (.\fter 
Hall.) Trenton limestone at Minneapolis, Minn. Collection of C. Schuchert. 
