1893.] Recent Literature. 1081 
Machaeracanthus is also referred tothis order. The author accepts 
the reference of the Acanthodii to the Elasmobranchii. 
Dr. Fritsch makesthe important discovery of the scales of Ceratodus, 
which resemble those of the existing species. 
The present work is the most important one of modern times in 
the amount of light which is thrown on the structure of the primitive 
fishes. —E. D. Cope. : 
Fic. 1.—4 gió fin of Xenacanthus 
(Pleuracanthus). B Cephalic spine. 
Tooth; C’ Tooth magnified. D Gill pric- 
kles; all of Xenacanthus (Pleuracanthus). 
EXPLANATION OF PLATES. 
Plate XXIX. Xenacanthus dechenii Goldf; from Fritsch. 
Plate XXX. Trissolepis kounoviensis Fritsch ; from Fritsch. 
