54 Field Museum of Natural History — Geology, Vol. IV. 



Locality and horizon. — This species was originally described from 

 the Cincinnati shales of Carroll and Kendall Counties, Illinois. It has 

 been collected by the writer from the Lower Maquoketa beds at Cler- 

 mont, Elgin, and Bloomfield, Iowa, and Upper Maquoketa bed at 

 Patterson's Springs near Brainard, Iowa. 



Genus BUMASTUS Murchison 1839. 



"General characters. — Pars anterior; capitis rotundato-convexa, 

 subcequalis; oculis lunatis, glabris, remotis. Pars costalis s. corpus, sulcis 

 longitudinalibus vix apparentibus, costis decern. Pars posterior maxima, 

 rotundato-tumida, cequalis. Omnes testes partes ultro citroque, linear um 

 sulcatarum subtilisimis ambagibus punctulisque confertis, insignitee." 

 Silurian System 1839, p. 656. 



(translation) 



Generic characters. — Anterior part; (cephalon) rotund, convexity 

 of the head subuniform; eyes lunate, smooth, situated far apart. Seg- 

 mented part of the body; (thorax) longitudinal furrows scarcely dis- 

 cernible, ten segments. Posterior part (pygidium) large, roundly, 

 uniformly tumid. All parts of the test irregularly marked by impressed 

 lines, interspaces finely and obscurely punctate. 



The above is the original description of the genus. The author 

 states later that the surface markings may be of only specific importance 

 and that he has added them to the generic definition provisionally. 



Bumastus beckeri sp. nov. Plate XIV, Figs. 1-4. 



Type specimens: holotype in collection of Mr. A. G. Becker, one 

 paratype in collection of State University of Iowa, and the other 

 No. P 16708 Field Museum. 



Description. — Body oblong, slightly ovate, width at the genal 

 angles about half the entire length. Dorsal furrows nearly obsolete on 

 the cephalon and thorax and entirely so on the pygidium. Surface, 

 except in the region of the palpebral lobes, dorsal furrows and the 

 anterior central portion of the glabella, marked with indented, trans- 

 verse lines, more or less parallel to each other and to the transverse 

 divisions of the test. These lines are conspicuous and close together on 

 the doublure, somewhat less so on the cephalon and anterior segments 

 of the thorax. On the posterior segments and pygidium they are in- 

 conspicuous and only discernible with a magnifier. 



Cephalon strongly convex, semicircular in outline; the location of 

 the dorsal furrows indicated by two almost imperceptible grooves 



