Raymonp.— Isotelus gigas Dekay 
PLATE 2. 
Fig 1.— Basilicus barrandi (Hall). The imperfect cranidium which was the 
type of Asaphus wisconsensis Walcott. From the Leray-Black — 
River at Newport, N. Y. xX 3. No. 47, M.C.Z., Walcott coll. — 
Fig. 2-5.— Isotelus gigas Dekay. Young specimens in various stages of 
growth, illustrating the change from the rounded to the pointed 
pygidium and the shortening of the genal spines. From the 
Trenton at Trenton Falls, N. Y. xX %. No. 48, 38, 39, 40, 
M. C. Z., Walcott coll. | 
Fig. 6.— Isotelus iowensis Owen. An imperfect specimen from an unknown 
locality in Iowa. To be compared with a young Jsotelus gigas 
from Trenton Falls (fig. 5) and with a young J. iowensis from the 
same locality (Plate 3, fig. 2). x $. No. 420, M. C. Z., ? Si 
Charles Lyell coll. , a, | 
Fig. 7— Basilicus barrandi (Hall). The specimen which was the type © 
Asaphus romingeri Walcott. From the Leray-Black River : 
Newport, N.Y. x 2. No.35,M.C.Z., Walcott coll. . 
