L18 PALMONTOLOGY OF NEW YORK. 



angulated along the axial line, each sometimes hearing a moderately strong 

 tubercle. 



Pleura depressed in a more or less abrupt curve to the margin, bearing 

 eleven or twelve flattened annulations, which are separated by moderately 

 strong sulci. Each annulation is faintly grooved by a fine impressed line, 

 which is sometimes almost or quite obsolete. Border broad, becoming exca- 

 vate and slightly reflexed posteriorly; all the annulations except two becom- 

 ing obsolete upon reaching it. 



Doublure broad, reaching to the termination of the axis. 



Surface Ornamentation. The cephalon is covered with low tubercles which 

 become obsolete upon the anterior portion of the glabella and the depressed 

 areas of the cheeks. Upon the thorax and pygidium each segment and 

 annulation is ornamented with granules; these upon the latter sometimes 

 appear to be arranged in two rows, one upon each limb of the pleural annu- 

 lations. In rare examples a row of small tubercles is noticeable along the 

 axial line on both thorax and pygidium, beginning with a faint tubercle upon 

 I he occipital ring, the next being at the third or fourth segment, thence 

 backward becoming stronger toward the apex of the axis. 



Dimensions. An average individual measures : 



Body. Cephalon. Thorax. Pygidium. 



Length 37 mm. 13 mm. 11mm. 13 mm. 



Width 24 mm. 24 mm. 22 mm. 21mm. 



The largesl entire individual observed has a length of 60 mm. and a width 

 of 40 mm. 



Observations. Entire individuals of Proetus macrocephalus are of rare occur- 

 rence, and the crust is so delicate and tenuous that when the parts are in 

 juxtaposition, it is usually broken away. The symphysis along the facial 

 sutures appears to have been very free, for the movable cheeks are usually de- 

 tached, and of several hundred specimens of the species which have passed 

 under observation but a single example retains all the parts. 



