The IntxiiiieHcens Fauna. — Clarke. 103 
Hamilton. The Interstrialis race is recognized in our Cliemung 
Stropliodonta cayuta and in the upper and middle Devonian of 
Europe and the east in Struphomena duterti-ii and S. aselli." It is, 
however, a fact that S. incBquistriata, S. cayuta and S. dutertrii 
represent a subordinate tj'pe of structure which has been desig- 
nated by (Ehlert with the term DouviUina. ^Vhether *S'. inter- 
strialis and *S'. aselli belong to the same group we have no definite 
evidence. It is further stated that in the European '-race" (re- 
ferring to the convexo-concave strophodontoids,) the terminations 
of the hinge develop into slender, mucronate points ; that in the 
American "race" (the flat group?) "these mucronate points Jirst 
appear in the Tully limestone forms and are characteristic of the 
race afterward till it ceases. The representatives of this (mucro- 
nate) type of StropJiomena are common in Europe throughout the 
Devonian, going under the specific names interstrialis, aselli and 
dutertrii, and the conspicuous development of the mucronate 
points did not appear till about the stage of the appearance of 
Rhynchonella cuboides." This argument is not a forcible one ; it 
is weakened, in the first place, by being based on distinct subor- 
dinate types of generic structure, and further, we might cite 
Strophodonta Junia Hall, of the Hamilton group as an example of 
a species which frec^uentl}' shows mucronate cardinal extremities, 
and to go back to the inceptive forms of the strophodontoid type, 
S. leda Billings, has these extremities strikingly developed, and 
this is a form which differs no more widel}' from S. demissa, the 
type of the genus Sfrophodontn than do the subordinate t3'pes of 
^S*. perplana and S. dutertrii. The species Stropliomena arniata 
and S. stephani Barrande, from the etage F. , are strophodontoids 
withe xtended cardinal angles. 
It is upon these two forms, Orthis tuUiensis and Strophodonta 
perplana, var. tuUiensis, together with Rhynchonella ciiboides- 
venustida, that the correlation of the Tulh' with the Cuboides 
zone is based. ( )ne other direct comparison is instituted between 
the Tulh' and the Cuboides species. In reference to Bronteus 
tullius Hall, it is said that it "is closely allied to a form of the 
European Cuboides zone (/^. jlabelli/er GroMt)." But B. Tullius 
belongs to the subgenus Thysanopeltis (with spinous pygidial 
margin) and B. fiabellifer does not. 
It does not appear that there is much reason for regarding the 
coiTespondence of the Cuboides fauna and that of the Tully as 
greatly fortified by this evidence. The bond between tlio two is 
