422 Reviews—C. Brongniart—On Pleuracanthus. 
The following table is given by the author to show the equivalents 
of the Cambrian strata of the Baltic provinces with those of Norway 
and Sweden. 
Batic. SWEDEN. Norway. 
Dietyonema-shale Dictyonema-shale Dictyonema-shale.—2e 
Unguliten-sand 2d 
2 
Olenus-zone Olenus-zone an 
2a 
Paradoxides-zone Paradoxides-zone id 
Olenellus-zone. 
Zone of O. Kjerulfi Zone of O. Kjerulfi.—1b 
Fucoid-sand Fucoid-sandstone. 
Zone of Olen. Mickwitzi  Eophyton-sandstone Ta 
Blue Clay Sparagmit-stage | 
Lower Sandstone 
Fr. Schmidt thinks that the Baltic Olenellus zone is equivalent to 
the lower part of the St. John’s group in North America, and to the 
lowest stages of our Harlech and Longmynd groups, in which no 
Trilobites have as yet been found, whilst the Dictyonema shales and 
the Unguliten sand may be paralleled with the Lingula Flags. 
dey Jet WS JB OS We Se 
I.—M. Cuaritres Broneniart on PLevRACANTHUS.! 
HE precise characters of the extinct cartilaginous fishes, whose 
detached teeth and spines have long been known under 
provisional names, are now becoming gradually revealed through 
the progress of research; and no more interesting and important 
discovery has been made of late than that of the complete trunk of 
Pleuracanthus, described last April by M. Charles Brongniart, of the 
Paris Museum of Natural History. Through the kindness of M. 
Brongniart we are enabled to present the accompanying woodcut, 
which is a restoration of the skeleton of the fish, based upon no 
less than twenty-three examples of a new species (Plewracanthus 
Gaudryi), from the Coal-measures of Commentry, Allier, France. 
The known individuals vary in length from 0:45 m. to 1 m., pre- 
sumably owing only to their differences in age; the skeleton is 
always well displayed, being calcified as in Selachians, while the 
skin is destitute of shagreen. The body is elongate in form, and 
the snout obtuse. The notochord is persistent, and the bases of the 
neural and hemal arches expanded; the slender neural spines 
bifurcate distally in the greater part of the abdominal, and the 
anterior half of the caudal, region. ‘The pectoral fin, as already 
pointed out by Goldfuss and Anton Fritsch, is a biserial archiptery- 
gium; and each of the pelvic fins in the male is provided with 
a robust clasper, as in Chimeeroids and Selachians. The barbed 
spine is placed upon the head, and forms the anterior border of a 
small “cephalic” fin; and a long dorsal fin commences almost 
' “Sur un nouveau Poisson fossile du terrain houiller de Commentry (Allier),”’ 
Comptes Rendus, April 23rd, 1888. 
