236 E.. Billings on the Genus Centronella. 
Art. XXIIT.—On the genus Centronella, with remarks on some 
other genera of Brachiopoda; by EK. BiLuines.—In a letter 
addressed to the Editors of this Journal. 
Gentlemen :—As I fear that some confusion may arise with re- 
gard to the characters of the genus Centronella, I shall feel obliged 
by your permitting me to publish the original figures illustrating 
it, together with some others. 
i zs. 1, 2, 8. Ventral, lateral, and dorsal views of Centronella glans-fagea,—Fig. 4. 
Interior of dorsal valve, showing the loop—Fig. 5. Longitudinal section, showi 
oe Page of the loop in the interior.—Figs. 6,7. Figures 4 and 5 as copied by 
rof, Ha 
his at the most would be only a specific difference, but I have 
now some evidence that in C. glans-fagea the plate, when perfect, 
is as large as in @. Julia. I have lately succeeded in dissolving 
out four other specimens, showing the loop. ‘T'wo of these are, 
1 For Professor Hall’s paper, referred to here and elsewhere in this article, se 
this Journal, [2]. xxxv, See aaa xxxvi, 11, ' 
