ON THE OCCHREENCE OF 8TR0PE0DUS RIGAUXI 
(8AUV.J IN THE YORKSHIRE CORNBRASH. 
While at Scarborougli, during the present summer, I had 
the good fortune to find a tooth of a Cestraciontid fish in the 
Cornhrash on the north side of the Cliff. In determining the 
species, however, I encountered certain difiS-Culties ; hut before 
dwelling upon these, it is perhaps advisable to give a short 
description of the genus Strophodiis and an account of its 
range in time. 
The genus is essentially Mesozoic: it ranges from the Trias 
to Upper Cretaceous. The earliest species known is S. angm- 
tissimus of the Muschelkalk : the so-called Strophodus arcuatus 
from the Kuperschiefer of Riechelsdorf is not a Strophodus ; it 
belongs to the genus Wodnika (Miinster).* In general appear¬ 
ance the teeth of Stojohodus are very like those of Psammodiis ; 
and, for a long time, specie?, of the former were included 
in the latter. In connection with this point it is noteworthy 
that the earliest species of Strophodus (from the Muschelkalk) 
are of small size,—small compared with the Lower Oolite 
species, and very small compared with those found in the 
Carboniferous Limestone. This would of itself negative the 
idea of the direct descent of Strophodus from Psammodus, 
and would point to profound modification of type. But^ 
besides this, there are considerable differences of arrangement 
in the dentition of the two genera; indeed most ichthyologists 
now agree in removing Psammodus from the Cestraciontidoe. 
The following is a list of the species at present recognised as 
belonging to Strophodus in the British (Natural History) 
Museum Collection. 
S. angustissimus. Mil. Muschekalk, Jena, &c. 
S.favosus. Ag. Inferior Oolite (Dundry ). 
Great Oolite (Stonesfield). 
Forest Marble (Malmesbury). 
S. tenuis. Ag. Great Oolite and Forest Marble. 
* Beitr. YI. tab. 1., fig. 1 ; also Giebel, Fauna d. Vorw. I., p. 329. 
