On Lingulasma , Etc .— TJlrich. 
379 
Fig. 1 6. Dorsal side of same, showing, where the shell is removed, 
the median septum and traces of the scars of the muscular system. 
Fig. 1 c. Longitudinal section of same to show convexity of valves. 
Fig. 2. Lingula bisulcata Ulrich. Collection of Mr. C. Schuchert. 
Fig. 3 and 3a. A large ventral or pedicle valve of Lingula whitfieldi 
Ulrich, preserving only a small portion of the exterior layer of the 
shell. Collection of Mr. Charles Schuchert. 
Fig. 3 b. Interior of a small dorsal (?) valve of same showing indis¬ 
tinct muscular impressions and the pitted surface. Collection of Mr. 
C. Schuchert. 
Fig. 4, 4 a, 4 b. Three specimens of Lingula modesta Ulrich, showing 
extremes of size and slight variations in the former. 
Fig. 5. Gutta percha impression taken from the dorsal or brachial 
side of a nearly perfect cast of the interior of Lingulasma schucherti 
Ulrich, collected at Wilmington, Ill., and now belonging to Mr. C. 
Schuchert’s collection, a, posterior transverse ridge (? crescent); b, 
subcardinal scars ; n, umbolateral scars ; p, post-median scars; l, later¬ 
al scars; m, median scars; n, anterior scars; t, transverse scars; s, 
median plate or septum. 
Fig. 5 a. Gutta percha impressions of the pedicle valve of same. 
The figure is restored at the beak, the portion above the line being 
broken away in the specimen. 
5 c. Longitudinal section of same showing elevation of platforms 
and median plate. 
5 d. Surface of the shell of same x 8. The upper half represents the 
appearance on the lateral slopes, while the lower half does the same 
for the striae near the front. 
Fig. 6. Dorsal and profile views of a medium size specimen of Trem¬ 
atis fragilis Ulrich. Collection of Mr. C. Schuchert. 
Fig. 7. Dorsal valve of Trematis crassipuncta Ulrich. The reticula¬ 
tion at the front and sides is represented too fine in the figure. 
Fig. 7 a. Surface of same x 8. The shell is gone save in the de¬ 
pressed spaces, where it is marked with fine transverse lines. 
Fig. 8. View of a dorsal valve of an elongated example of Trematis 
umbonata Ulrich. 
Fig. 8a. Profile view of same. 
“ 8 6. View of the ventral side of a shorter shell of this species, 
and a longitudinal section of same. 
Fig. 8 c. Surface of same, x 8, showing the minute character and 
Arrangement of the punctures. 
Fig. 9. Gutta percha mould of a dorsal valve of Trematis oblata 
Ulrich ; whole external form had been preserved by being grown over 
by a bryozoan. 
Fig. 9 a. Profile view of same. 
“ 9 6. Ventral valve of same. A little more circular than usual. 
A specimen of medium size is 18 mm. long, 10.5 mm. wide 
and nearly 5 mm. in thickness (i. e. both valves). 
When the shell is exfoliated, the ventral valve exhibits a 
semi-circular band, situated a short distance in front of the 
centre, from which short lines radiate outward and forward. 
Just behind the middle a similar band, but without the radial 
fringe, is traceable. In the dorsal valve a median septum ex¬ 
tends nearly" to the front margin. Some of the muscular im¬ 
pressions as shown in fig. 1 b can be made out, but the ap- 
