MARCOU: THE JURA OE TEXAS. 
151 
A monograph, entitled The invertebrate paleontology of the 
Trinity division, was published in June, 1893, by Mr. Hill in the 
Proceedings of the biological society of Washington, vol. 8, p. 9-40. 
In this paper the author boldly declares that the Trinity division is 
Cretaceous, the lowest faunas resembling: and having* “ remarkable 
liomotaxial similarity with the Lower Neocomian, and the upper 
Glen Rose beds being referred to the Middle and Upper Neocomian 
of the Jura.” In all the forms published by Mr. Hill or quoted from 
his previous work on the Arkansas survey, there is not a single one 
which can be called a truly characteristic Neocomian fossil; while on 
the contrary all, with only two exceptions, are most characteristic 
Jurassic fossils. The only exceptions are two species of Monopleura 
and one species of Requienia. In the Jura Mountains Monopleura 
occurs in the first beds of the Lower Neocomian in contact with the 
Upper Jura, at Arzier, Canton de Yaud, where I collected it many 
years ago. As for the solitary Requienia of the Trinity division, it 
may prove to be a new genus related to Diceras of the corallian Jura 
and to Requienia, one of those evolutionary forms so often quoted by 
transformists. 
It is useless to repeat my views in regard to each of the forms 
found by Mr. Hill in the Trinity division ; Ammonites, gasteropods, 
and Lamellibrancliiae are all characteristic Jurassic fossils. The 
vertebrates are Jurassic dinosaurians and crocodilians; as for the 
plants, they are Cycadae, like the Cycadae of Portland, ferns, 
conifers, and Equisetae, a remarkably Jurassic flora. 
To say that the Trinity division represents in America the 
Neocomian of the Jura is a new attempt to classify the Tithonic with 
the Cretaceous series instead of the Jurassic. No one who has 
studied the Neocomian of Europe in the field will synchronize with 
it the Trinity division of Texas. 
In the Fourth annual report of the geological survey of Texas, 
under the title Invertebrate paleontology of the Texas Cretaceous, 
Mr. F. W. Cragin published in June, 1893, a number of species from 
the Trinity division, called by him “alternating beds of the Glen 
Rose, Bosque Division.” Only three are identical with Mr. Hill’s 
species. Many are new species, and some are so Jurassic in form, 
according to his own opinion, that he formed the curious specific 
name of jurafacies for a Homomya and a Modiola. Nevertheless, 
he puts all the fossils from the alternating beds of Glen Rose into 
the Cretaceous series. 
