1895. ] NEW YORK ACADEMY OF SCIENCES. 151 
no example of this genus has been found among the trilobites of 
Band 6. Hence, though the Protolenus Fauna holds the place 
where we might naturally look for Olenellus, this genus is absent, 
and as so many of the genera associated with it are also absent, 
we cannot regard this fauna as the Fauna of Olenellus. 
Of the genera of trilobites that are present Micmacca has close 
relationship with Zacanthoides; it differs in the course of the 
posterior extension of the dorsal suture. The relation will 
seem closer if we suppose a movement of the eyelobe during the 
growth of the individual in Zacanthoides, similar to that which 
occurred with the Ptychoparida, in which there was a contrac- 
tion of the eyelobe toward the glabella during growth and at 
the same time a projection. of the posterior extension of the 
dorsal suture outward, toward the genal angle. If this relation 
should be established, Micmacca may be looked upon as an an- 
cestral form of Zacanthoides. 
It is worthy of note that in two of the genera of trilobites that 
occur in the Protolenus Fauna, the earlier species are larger than 
the later, as though these genera had reached their culminating 
point, and were on the decline; these types are Bergeronia and 
Ellipsocephalus ; and as regards the latter, the continued dimi- 
nution in size is notable in the sole species of this type in the 
Paradoxides Zone, viz.: EH. Hoffi.* 
Among the Ostracoda of this fauna, a diminution in size is 
found in the successive species of Hipponicharion, and of one 
section of Beyrichona (e. g.,planata and tinea). The former ge- 
nus is among the first crustacean remains of these Cambrian beds. 
In this fauna we find ourselves among a very primitive as- 
semblage of Brachiopods, for among them are forms which it is 
difficult to assign to any known genus. Many are small, some 
are minute, and the larger forms all belong to the Obolide and 
Siphonotretidz. One of the latter is remarkable as being of the 
inarticulate order, yet having a distinct articulation at the hinge- 
line. 
The Gasteropoda are all of aberrant types. This class is 
chiefly represented by various forms of Hyolithidz, the most 
ancient of all known types of Gasteropods, having come down 
to this fauna from Pre-Cambrian times.t A very remarkable 
form of this fauna is Pelagiella, which is probably an oceanic 
Heteropod of large size. The mouth of the shell is such as no 
crawling mollusc would have possessed. 
Finally may be mentioned the Foraminifera, of whicb several 
genera are present, the most common being Orbulina and Globi- 
* EB. Germari of Bohemia is too aberrant to be included with the earlier types. 
+ It is represented by Orthotheca in the Etcheminian series, 1200 feet below. 
