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BULLETIN OF THE LABORATORIES 
approach the latter specimen, although sometimes quite convex and 
more or less arched anteriorly. Associated with these pygidia are gla- 
bellse, which would be referred to IllcEnus ambiguus without hesitation, 
if the corresponding pygidia were found. However the following 
slight distinctions may be discovered. The anterior margin is less 
curved, the curve of the facial suture anterior to the palpebral lobe is 
less marked, the glabella is less convex, especially along the median line. 
All of these characters in themselves would hardly give rise to a new 
species. Whether there are two species with different pygidia, but 
very similar glabellae, is unknown. If not, the glabellae of Brown’s 
Quarry must be referred to lUcemis ambiguus. Lieut. A. W. Vogdes 
writes to me, as Prof. Whitfield’s opinion, that the pygidia are related to 
those of IllcEniLs insignis, Hall^ as figured in N. Y. Report of State Cab. 
20. But these evidently do not belong to the glabella which typifies the 
species. Hence in either case the affinity of the pygidia of Brown’s 
Quarry remains undecided. More material is perhaps necessary to 
determine this question definitely. 
Locality and position. Huffman’s Quarry, Stolz’s Quarry, Brown’s 
Quarry, Clinton Group. 
VI. Ill^nus ambiguus, Foerste. 
' This species was founded upon a number of pygidia and gla- 
bellas which have a wide range and are usually found associated to- 
gether. In the first paper, figure loc, of plate XIV, is inaccurate, 
representing the upper length of the grooves as being very distinct, 
whereas in reality this part is very faint and the pits at the extremity 
of the grooves seem to be isolated, if the glabellae be not carefully ex- 
amined. 
Locality and position. Soldiers’ Home Quarries, Fauver’s Quarry 
(pygidium and fragment of glabella), Fair Haven (pygidium). Clin- 
ton Group. 
A hypostoma, not very unlike that figured by Billings under 
Asaphus Pelops., is found at the Soldiers’ Home (Plate VHI, Fig. ii). 
I am uncertain with what Clinton forms to place it. It is certain at 
least that the hypostomae of the genus Illaenus figured by Gerhard 
Holm, in his work on the Swedish species, are very unlike the hypos- 
toma in question. 
