NOTES ON PALEOZOIC CRUSTACEA, No. 5. — 

 CARBONIFEROUS TRILOBITES FROM MISSOURI. 



BY ANTHONY W. VOGDES. 



Among a large number of trilobites lately 

 sent me by Prof. G. C. Broadhead, from the 

 Chouteau limestone of Providence and Sedalia, 

 Missouri, there are several specimens of smooth 

 pygidia, which may be classed as new to sci- 

 ience. Although this characteristic is known 

 to several genera of fossil Crustacea, it is uncommon. 

 We recall Calymene Arago and C. S alter i Rouault, from 

 the Silurian of France; Proetus crassimargo Roemer, 

 from the Devonian of Germany, and Proetus ? levis 

 Woodward, from the Carboniferous of England. 



The German species was first described by F. A. 

 Roemer, in Palseontographica, Bd. 2, s. 65, tab. x, fig. 9, 

 from several fragments. The author remarks regarding 

 the pygidium, that "The axis of the pygidium exhibits 

 three distinct and indications of seven more rings, the 

 lateral lobes near the upper edge slightly indicate three 

 pleurse; the other part is smooth, but shows at the lower 

 edge indications of ribs." 



In the reclassification of this species by Novak, in 

 Dames and Kayser's Palasont., Bd. 1, Heft 3, s. 44, it is 

 divided into three species, namely: Proetus crassimargo 

 Roemer, P. Frechi Novak, and P. orbitatus Barr. 



Novak says that Proetus crassimargo belongs to the 

 ten-jointed Proetida?, typical of the group Proetus orbita- 

 tus. The head differs from the latter by being less arched, 

 by a narrower glabella, which is more pointed in front, 

 slightly compressed between the anterior ends of the 

 palpebral lobes, and bordered by less convex dorsal fur- 

 rows. It is also more distinctly marked with side furrows, 

 eyes larger, and by a node which is not at the posterior 

 edge, but in the middle of the neck ring; also by the 



Proc. Cal. Acad. Sci., 2d Ser., Vol. VI. June 24, 1896. 



