OE DENISON UNIVERSITY. 
125 
cheeks posterior to the grooves have but few tubercles and these are 
also small. The occipital furrow is well marked, and the occipital 
occipital margin is raised and distinct. The thorax is composed of 
twelve segments. The middle lobe is about three-fifths as wide as the 
lateral lobes. If characterized by well marked tubercles the speci- 
mens before us do not show them. The pygidium is triangular, 
broader than long, in the ratio of seven to five. The central lobe an- 
teriorly is equal to about half the breadth of the lateral lobes. The 
lateral lobes with nine distinct anchylosed segments, with a possible 
tenth. These apparently without tubercles. The middle lobes with 
about twenty-eight transverse ridges. In casts these are broken or 
even indistinct along the middle of the lobes. Beginning with the 
fourth ridge every fourth succeeding ridge bears a tubercle at the 
middle. While studying the EncrinuridcF, the question has often raised 
itself whether tubercles prominent in the cast might not be entirely 
absent on the surface of the pygidium itself but unfortunately we have 
never had the proper material to determine this question. 
Two species closely related to E. Mitckelli have already been 
described from Australia by Mr. L. G. DeKoninck. The first is 
Cromus Bohemiciis^ Barrande. A comparison with the Bohemian 
species however shows marked differences. The large tubercles at the 
dorsal suture are in the Bohemian species represented as lobes with 
the smaller tubercles of the remainder of the glabella also present 
on them. The eyes are farther removed from the occipital furrow. 
There are twelve well marked ridges on the lateral lobes of the pygid- 
ium, the summit of which is represented as being flat while in ours 
they are distinctly rounded. The sides of the pygidium are also rep- 
resented as being denticulated; in our specimens traces of a similar 
structure are visible but they are not sufficiently distinct for delinea- 
tion. The description of the specimens from Yarralumla makes it 
probable that these are also distinct although closely related. 
The pygidium of the second species described, Cromus Murchisoni^ 
L. G. De Koninck is said in the text not to have been found. The 
pygidium figured in the plate and mentioned in the explanation ot the 
same, undoubtedly was associated by him with his Encrinurus Bar- 
randei of the same plate, and agrees well with his description of that 
species. Cromus Murchisoni is readily distinguished from our species 
by the absence of the large tubercles along the dorsal furrow, the ar- 
rangement of the posterior tubercles in transverse rows (a fact not 
