128 PALEONTOLOGY OF NEW YORK. 



have a forward Bend near the axial furrows and a slightly retral curve over 

 the median line. 



Pleura evenly convex and bearing from six to eight annulations, each of 

 which is grooved by a finely impressed line. All the annulations become 

 extinct upon reaching the border. 



Surface Ornamentation. Upon the cephalon and thorax the test is covered 

 with faint, nearly obsolete pustules or granulations, which seem to be want- 

 ing upon the pygidium, except at the posterior edges of the axial annula- 

 tions. The last four or five segments of the thorax each bear a strong 

 tubercle in the axial line, as in Proitus Rowi. A faint axial tubercle is also 

 visible upon the occipital ring. 



Dimensions. An entire individual of normal proportions measures : 



Body. Cephalon. Thorax. Pygidium. 



Length 37 mm. 14 mm. 13 mm. 10 mm. 



Width 26 mm. 26 mm. 20 mm. 19 mm. 



Observations. The Proitus Davenportensis of Barris, appears to be identical 

 with Shumard's type, and the description here given is from Mr. Barris' original 

 specimens, which he has kindly loaned for the purpose. 



Proitus Prouti may be regarded as a western representative of the type of 

 Prortus, exemplified by the New York species, P. angustifrons, P. clarus and P. 

 Rowi. With the last named species it has many points of close similarity, both 

 in general contour and in details. It will be found, however, to differ in the 

 following particulars, which, taken together, prove of specific value: the cephalic 

 border is broader and more conspicuously grooved; the genal spines very much 

 longer; the axis, both upon the thorax and pygidium, narrower; the pygidium 

 more evenly convex, and with a more conspicuous border. 



Distribution. Hamilton group. In the fawn-colored limestone, near Daven- 

 port, Iowa. 



