222 The American Geologist. October, 18% 
8. Development of the Pli!fsio(/ra}>hi/ of California. James Pebuin 
Smith. This paper was illustrated by a stereopticon view of a relief 
map. The present contour was ascribed mainly to Tertiary and Qua- 
ternary uplifts and consequent erosion. 
.9. Synopsis of California Stvatigrapliy. James Perrin Smith. 
10. Ancient and Modern Sharks, and the Evolution of the Class. E. 
W. Claypole. The Devonian cladodout sharks, recently discovered in 
northern Ohio by Dr. Clark and described by the author in a series of" 
papers in the Am. Geologist, exhibit great differences from their mod- 
ern representatives ; and this paper presented some suggestions on the 
probable ways in which these differences have been evolved. 
11. Observations on the Dorsal Shields in. the Dinichthyids. Charles 
R. Eastman. The object of this paper was to trace the genetic rela- 
tionship between the typical dinichthyid genera of America and the 
European coccosteids. Attention was called to the fact that valuable 
systematic characters are afforded by the configuration of the median 
dorsal plate in the Coccosteidfe. In particular it was maintained that 
a large, excavated posterior process is common to dinichthyid but ab- 
sent in coceosteid genera; and, furthermore, that the coccosteids may 
be arranged in a definite series according to the progressive modifica- 
tion of the inferior ridge and terminal process of the dorsal shield. This 
series includes the genera Coccosteus, Homosteus and Heierosteiis, to- 
gether with certain forms leading up to Dinichthys. the affinities of 
which do not seem to have been properly understood. Among the latter 
may be mentioned the so-called Pelecyphorus of Trautschold, Asterolejns 
hohemica of Barrande, Coeeosteus sp. {=D. livonicus) of Pander, and 
one or two as yet undescribed forms from the Devonian of the Eifel 
district; all of which are shown, by their possession of a characteristic 
terminal process, to belong to the dinichthyid instead of the coceos- 
teid group. 
The series of European dinichthyids, starting with Pander's D. livo- 
nicus, may be traced from its probable origin in northern Europe south- 
ward and eastward into Bohemia and Russia, westward into central 
Germany and Belgium, and thence across the Atlantic into the United 
States and Canada. At least one species {D. tuherenlatus) is intercon- 
tinental in distribution. Westward the divergence was so great as to 
give rise to no less than fifteen species of Dinichthys, besides a number 
of related genera; and the most remarkable fact concerning them is 
their prodigious increase in size. The function of the posterior process 
was assumed to be in relation with swimming; and with its gradual 
development, increased locomotive facilities were acquired. The known 
predacious habits of Dinichthys afforded it the necessary competition, 
and its better equipment for swimming enabled it to attain the ascend- 
ancy over the original coceosteid stock. Its ultimate supremacy in 
Devonian seas is witnessed V)y its size, its abundance and distribution, 
and its range of variatiim. 
Incidentally a slab was exhibited on.which was preserved the entire 
ventral armor of a Dinichthys from the Portage shale near Buffalo, dis- 
