OF DENISON UNIVERSITY. 
109 
branches where they are well preserved, are from .5 mm, to .65 mm. 
wide. The dissepiments vary from .1 mm. to .22 mm. in thickness. 
The name signifies ladder shaped. 
This species is evidently related to Dictyonema retiforme. Hall., dif- 
fering from the ?ame in the narrower branches being more compactly 
arranged, the dissepiments likewise occurring at shorter intervals. Ac- 
cording to Prof. J. W. Spencer the branches of D. retiforme are on an 
average about one millimetre in width. The largest branches of our 
specimens do not attain this width. 
Locality and position. Soldiers’ Home, Clinton Group. 
Graptolites of this genus usually appear as black strands on the 
surface of the rock. In this connection it is interesting to note that 
the cell walls of Stictopora gracilis, Spencer, present the same appear- 
ance, momentarily suggesting a graptolite. 
PLATE VIII. 
Fig. I. Acidaspis Oidoni, n. sp; a head, anterior margin unknown. 
Fig. 2. Proetus determinatus, n. sp; a glabella with part of anterior border. 
Fig. 3. Proetus determinatus, n. sp; a glabella, with attached border and pal- 
pebral lobe. 
Fig. 4. Phacops ptilchellus, n. sp;. an associated pygidium. 
Fig. 5. Proetus ; a glabella with anterior border and palpebral 
lobe. 
Fig. 6. Illcenus Daytouensis, Hall and Whitfield; rostrum in position, sharp 
edged postero- lateral margins of movable cheeks broken off ; a, a movable cheek, 
from Ludlow Falls. 
Fig. 7. Illeenus Madisonianus, Whitfield; a glabella, very doubtfully referred 
here. 
Fig. 8. Illcenus Madisonianus, Whitfield; pygidium, with paraboloid outline. 
Fig. 9. Illcenus Madisonianus, Whitfield; pygidium, somewhat broader. 
Fig. 10. Illcenus Madisonianus, Whitfield; pygidium, semi-circular, not parabo- 
loid . 
Fig. II. A hypostoma, very doubtfully referred to some species of Illaenus, 
Fig. 12. Calymene Vogdesi, n. sp; head of type S])ecimen. 
Fig. 13. Calymene Vogdesi, n. sp; profile along the middle of the same. 
Fig. 14. Calymene Vogdesi, n. sp; head of a younger specimen. 
Fig. 15. Caly 7 nene Vogdesi, n. sp; profile along, the middle of the same. 
Fig. 16. Calymene Vogdesi, 7 t. sp; characteristic pygidium. 
Fig. 17. Ceraurus ; a glabella. 
Fig. 18. Lichas breviceps. Hall; a glabella, with part of a fixed cheek. 
Fig. 19. Lichas breviceps, Hall; a hypostoma. 
