RaymMonv.— Isotelus gigas Dekay. 
EXPLANATION OF PLATES. 
PLATE 1. 
Fig. 1.— Isotelus gigas DeKay. An immature specimen with (apparen y) 
three segments in the thorax. From the Trenton at Trenton Fall 
N.Y. X15. No.45, M.C. Z., Walcott coll. ; 
Fig. 2— The same species. A Sanh oh eee but still immature individu: 
showing the short rounded pygidium of the young. Thora 
partially buried in the matrix. From the Trenton at Trente 
Falls, N. Y. X6. No. 48, M. C. Z., Walcott coll. 
Fig. 3— Isotelus maximus ? Locke. The type of Proétus spurlocki Mee 
From the Eden at Cincinnati, Ohio. X 6. No. 43, M. C. i 
Dyer coll. 
Fig. 4— Basilicus barrandi (Hall). A specimen with a narrow ‘bide simil 3 
to the type of Asaphus romingerit Walcott. From the Lerat 
Black River at Newport, N.Y. > 3. No. 46, M.C. Z., Waleo 
coll. 
Fig. 5— The same species. A nearly complete but flattened specimen some 
what restored about the eyes and at the posterior end of the pyé 
dium. From the Black River at the quarry on Limestone Cree 
near Platteville, Wisc., the type locality of the species. :- 
No. 34, M. C. Z., Whitney coll. 
