30 The American Genloyist. -inly, is% 
nelluii beds iicnr 'I'l-oy. X. Y. Hiiviii^' lately cxaiiiined these 
in connection with a study of the species of this genus, i'ouiid 
In the Piu-rtdoxides zone, I have had occasion to pen the I'ol- 
h)wing note : 
Microd/scus lohatus Hall. 
Among- Mr. Schuchert's fossils were a number of trilohite 
shields bearing the above name, and among them a good ex- 
ample corresponding to the tigure and description of the head- 
shield of that sjiecies, as given by Mr. Walcott. The example, 
however, is considerably larger than the one described by that 
author,* and the furrows of the glabella not so distinct as 
represented in the description. 
In the "Fauna of the Olenellus zcme" Mr. Walcott says the 
tigure referred to M. lobafvts, fig. if/, is probably that -of a 
young specimen of 3f. speciosns; but the example of J/, lolxi- 
ti(.s received from Mr. Schuchert very nearly corresponds to 
this figure, and yet is nearly as large as the' adult shield of 
ilf. speciosi'n represented by tigure ;5r.f I judge, therefore, 
that Mr. Walcott's first determination of fig. la as the head 
shield of M. lohatiis was correct, though it represents a young- 
individual, while flg.l is a still smaller head retaining embry- 
onic characters. Whatever may be the fact, fig. 1^/ very fairly 
represents the apjiearance of an exam])le of J/. Johafiis, head 
shield 4 mm. long. 
Among the fossils received from Mr. Schuchert were a num- 
ber of examples of a new species of Microdiscus, which is of 
considerable interest, as presenting in the Olenellus beds t\n 
ancestral type of the section J^Jod/sciis, which became so 
greatly expanded in the later (Paradoxides ) fauna. The fol- 
lowing are its characters: 
Microdiscus schucherli n. sp.J 
Head shield semicircular, one quarter wider than long, fiattened in 
front, drawn in and upturned at the genal angles: axis projecting be- 
hind. Anterior marginal fold enclosing at the front a flattened area, 
which is indented in front of the glabelhi. Glabella two-thirds of the 
length of the shield, cylindro-conical, depressed in front, elevated and 
projecting backward behind; three pairs of furrows faintly impress the 
sides. Occipital ring not visible. Cheeks moderately arched, not meet- 
'^U. S. Geol. Surv., Bull. 30, p. 15(5, pi. xvi. fig la. 
tU. S. Geol. Surv., Bull. 30, pi. xvi. 
JFigures of this sjjccies will probably appear in the Transactions of 
the New York Academy of Science. 
