90 
Gustaf T. Troedsson 
striation quite as B. avunculus Hadding or S inuitopsis neglecta Barr, but a little 
coarser. The section of the whorls seems to be the same as that of B. avunculus. 
Slitband lacking. Shell wall thin, most of the specimens are flattened by com- 
pression from various directions. 
Bellerophon (Sinuitopsis ?) subtrilobatus n. sp. 
PI. I, f. 15. 
Gradually enlarging, carinate volutions. The keel is rounded on the shell, 
more sharp and biconcave (»subtrilobate») on the casts. Section of whorl rhombic, 
most abruptly inflected at umbilicus. Slitband lacking. Shell thick, devoid of orna- 
mentation. Aperture not preserved. The figured specimen measures: Diameter 
4 mm., height 2 mm. (Another 9 resp. 5 mm.). 
Bellerophon (Bucaniella) atavus n. sp. 
PI. I, f. 16. 
Umbilicus moderately narrow and deep. The whorl is strongly trilobed, the 
median lobe largest with plane or slightly convex dorsum which has been more 
resistent to compression than the remaining shell, as on compressed specimens the 
edges of this wall appear as two narrow ribbons. These ribbons then do not belong 
to a slit baud, which is lacking here. Towards the aperture the whorl is gradually 
enlarging. The dimensions are seen on p. 41. 
Bucaniella atava is closely related to the American Clinton-Medina shell, Bucania 
trilobata Conrad but is narrower at the aperture than Sowjsrby’s Bellerophon trilo- 
batus of the correspondent age of Europe. 
Holopea Mobergi n. sp. 
PI. I, f. 17—18. 
Height 9 — 10 mm. Apical angle (60° — )75° — 80°. Volutions 4 — 5, well rouuded 
each of the lower ones being 1 ,5 times the height of the next above. The aperture 
is not preserved but to judge from the shape of the whorls it is nearly circular 
and without any emargination. Near the aperture a few specimens show close but 
coarse growth lines. The shell for the rest, when preserved, smooth and glossy, 
wholly devoid of ornamentation. H. Mobergi is related to the upper Ordovician 
species of N. America, indicated on p. 43. 
