Figs. 5 and 
oH 
Figs. 7 and 8. 
Fig. 9. 
Figs. 10 and 11. 
Fig. 12. 
Figs. 13 and 14. 
13. 
14. 
Figs. 15 to 18. 
15 and 16. 
WUE 
18. 
Figs. 19 to 22. 
19. 
20. 
PAU 
22. 
Figs. 23 and 24. 
23. 
24. 
_ 
a 
PLATH XXIX. 
LINGUA Ad ED ER BMVViliitflel dieiereais selenie sislaiielecisal- aclcleleleloje rise wisi) -cheles cis eG niwise nine 
Dorsal view of an exfoliated specimen to show the flattening along the lateral 
margins. Trenton limestone, Minneapolis, Minn. Minnesota Geological Sur- 
vey collection. 
Interior of the ventral valve, drawn from a natural cast, the usual mode of 
occurrence of this species. g, umbonal scar; h, central scars; k, middle laterals; 
ji, anterior lateral and transmedian scars; v, vascular sinuses; vs, vascular 
trunks. (After Whitfield.) 
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 letters 
as above. (After Whitfield.) 
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. 
TING UDA Eels Billings «fe en ccicene- seeteins meleielein eins celia) e]ejala\e\n\s\s)a we aieivivinininie ~ieinini= 
A dorsal valve with strong radiating lines in the anterior half. 
Profile outline of the same specimen. Trenton shales, Fremont, Winona county, 
Mion. Minnesota Geological Survey collection. 
LINGULA PHILOMELA BillingS..,........--s cece cece ence terete eee etree tees ee eens 
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. 
[bostequae/\ Ter swanoiavoter 1s HULA saeloeAgaonpore conse oe abbad JonceO cooseuboccsncocossoc 
Ventral valve, showing the rounded Obolella stage of growth in the posterior 
portion. Trenton shales, St. Paul, Minn. University of Minnesota collection. 
LINGULA RICINIFORMIS, var. GALENENSIS W. and S. .... .- eee ee cece eee ee eee e cere 
View of the ventral valve and profile outline of the same. Galena shales, near 
Kenyon, Minn. Collection of W. H. Scofield. 
LINGULA COBOURGENSIS Billings (?)............ececeeee cece ncn ce ceeeecteeesteens 
View of a specimen provisionally referred to this species. Trenton limestone, 
Chatfield, Minn. Minnesota Geological Survey collection. 
LINGULA (GLOSSINA) HURLBUTI N. H. Winchell ......-.-.. 0-0 sees eee eee e eee ee 
A view of the ventral (?) valve of the type specimen. 
Enlarged view of the concentric surface striz, x 23. Middle Galena, Mantorville, 
Minn. Minnesota Geological Survey collection. 
LINGULA (GLOSSINA) DEFLECTA W. and S......-.e ess ee cece eee eee e ete e eee c eee 
A dorsal valve and profile outline of the same. Galena shales, near Fountain, 
Minn. 
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. 
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. 
IDyaStetoADN TO), ADINeIG) CONG! oasy ndce no copoDadeddeo coopuocooood coUdoOnUtoUT coodecoonS 
‘* 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. 
Profile outline of the same specimen. Galena limestone, near Hader, Minn. 
Collection of W. H. Scofield. 
An internal view of the dorsal valve, taken from a gutta percha impression. 
h, central scars: s, septum; «, concentric laterals. (After Hall.) 
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. 
SIPHONOTRETA (?) MINNESOTENSIS Hall.........--.- 20 esse eer eee ee eee ee teen eeeeee 
View from the dorsal side of a specimen retaining the valves in juxtaposition 
and preserving most of the epidermal layer of the shell. 
The ventral valve of the same specimen, imperfect in the umbonal region. (After 
Hall.) Trenton limestone at Minneapolis, Minn. Collection of C. Schuchert, 
341 
342 
343 
344 
346 
347 
348 
349 
