1! PALEONTOLOGY OF NEW YORK. 



into spines having n length nearly equal to the length of the pleurae them- 

 selves. A >|'iiic similar to these, but shorter and relatively broader, is pro- 

 duced in the axial line, thus making eleven spines in the pygidial fimbria. 

 Some slighl variation is noticeable in the form of these spines, but in typical 

 examples, the ten lateral extensions of the fimbria are broad, short, flat and 

 closely set, the apex pointed backward, the terminal lobe being shorter 

 and linguiform. 



Bypostoma, elongate-sub-triangular; anterior angles auriculate, posterior ex- 

 tremity sub-linguiform. Centrum convex, bounded posteriorly by a conspi- 

 cuous sulcus. The postero-lateral pits on the centrum are joined by a faint 

 groove. Surface covered with venate lines and faintly granulose. 



Surface Ornamentation. In the normal forms of this species the entire sur- 

 face is covered with granulations which become quite strong on certain por- 

 tions, viz., the axial region of the glabella, and thorax, and the surface of the 

 pygidial fimbria, where the granules become elongate and pustuliform, often 

 crowded and more conspicuous than upon the surface of the shield itself 

 Upon the thoracic pleurae are single rows of low and inconspicuous pustules, 

 which, in somewhat weathered specimens from the shales, often appear as 

 shallow punctae. The occipital ring bears a strong central spiniform node, 

 and the thoracic segments along the axial line, sometimes evenly rounded, 

 are usually slightly angulated or nodose, the nodes becoming stronger toward 

 the pygidium. The annulations of the pygidium are evenly rounded. The 

 surface of the doublure is granulose. 



.->■ 



Variations from the type of Cryphaus Boothii, Green, as diagnosed by its 

 author, and as here described more at length, occur in a series of asso- 

 ciated forms presenting a marked and persistent deviation in certain 

 features. This is most noticeable in the character of the pygidial fimbria, 

 hut it appear.- that no variation has taken place in this feature without 

 correlative variation in certain other respects. In many individuals of this 

 sub-genus, particularly those occurring in the limestone layers in the Hamilton 



