1 PALEONTOLOGY OF NEW YORK. 



colossal size, which, judging from the proportions afforded by other specimens, 

 must have measured upwards of 200 mm. in length. 



Observations. There is a striking similarity in the specific details of Caly- 

 mene platys, Green, and those of Calymene Niagarensis, Hall. Indeed upon the 

 basis of any external feature, further than the great difference in size attained 

 by the two species, it might be difficult to establish the specific limitations. 

 Here, however, the notable diversity in the hypostomas proves of great import- 

 ance. In Calymene Niagarensis the hypostoma is elongate, with the anterior 

 margin entire, lateral margins broadly incurved and reflexed, sharply and 

 deeply emarginate behind, centrum convex and rounded, bounded by a strong 

 sulcus at its base, and bearing a conspicuous furrow on its posterior portion. 

 In respect to size, the largest individuals of Calymene Niagarensis will not exceed 

 "in nun. in length, and the smallest observed of Calymene platys do not fall 

 below 65 mm. in length, and as noticed, may have attained a length of 200 mm. 

 Murchison has figured a large individual of Calymene Blumenbachi, Brongniart, 

 which has a length of about 100 mm. (Silurian System, pi. vii, fig. 6), and 

 Angelin one of Calymene spectabilis, Angelin, 125 mm. in length (Palueontol. 

 Scandinavica, pi. xix, fig. 5). It is a noteworthy fact that the last known 

 representative of this characteristic Silurian genus, Calymene, should have attained 

 dimensions which surpass those of any of its known predecessors. 



Distribution. Upper Helderberg group. In the Schoharie grit, at Schoharie, 

 Schoharie county, and Knox, Albany county. In the Upper Helderberg lime- 

 stone, .it Falkirk and Clarence Hollow, Erie county, and Falls of the Ohio. 



IIOMALONOTUS, Kcenig. 1825. 



HOMALONOTUS MAJOR. 



PLATE V A, FIG. 1. 



hu major, Whitfield. Bulletin Amer. Mus. Nat. Hist., vol. i, No. 6, Art. xi, p. 193, pi. xxii. 



188H. 



Tie' Cephalon and anterior portion of the Thorax have not been observed. 

 Tie' Thorax has the lateral margins sloping somewhat less rapidly than in 

 Homalonotus Dekayi, and very much as in H. delphinocephalus. Surface flat, 



