OE DENISON UNIVERSITY. I 25 



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-fifihs 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. \\'hile studying the Encrinuridcp. 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 cpiestion. 



Two species closely related to E. Mitchelli have already been 

 described from Australia by Mr. L. G. DeKoninck. The first is 

 Cromits Bohemicus, Barra?ide. 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 gl.ibella 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 Varralumla makes it 

 probable that these are also distinct although closely related. 



The pygidium of the second species described, Cromus Murchisom, 

 L. G. De Koninck is said in the te.\t 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- 

 randeioi\\\^ same plate, and agrees well with his descrii)tion of that 

 species. Cromus Murchisoni is readily distinguished from our sj^ecies 

 by the absence of the large tubercles along the dorsal furrow, the ar- 

 rangement of the posterior tubercles in transverse rows (a fact not 



