4 
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 platijs, Green, and those of Cahjmene 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 Cahjmene 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 Cahjmene Niagarensis will not exceed 
50 mm. in length, and the smallest observed of Cahjmene platys do not fiill 
below 65 mm. in length, and as noticed, may have attained a length of 200 mm. 
Murchison has figured a large individual of Cahjmene BlumenbacM, 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 (Palaeontol. 
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, at Falkirk and Clarence Hollow, Erie county, and Falls of the Ohio. 
HOMALONOTUS, Kcenig. 1825. 
Homalonotus major. 
PLATE V A, FIG. 1. 
HomaloTwtus major, Whitfield. Bulletin Ainer. Mus. Nat. Hist., vol. i, No. 6, Art. xi, p. 193, pi. xxii. 
188ii. 
The Cephalon and anterior portion of the Thorax have not been observed. 
The Thorax has the lateral margins sloping somewhat less rapidly than in 
Homalonotus Dekayi, and very much as in H. delphinocephalus. Surface flat. 
