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NEW YORK STATE MUSEUM

of these fossils and possibly also graptolites that would indicate the age of the beds. They have indeed afforded a layer with an association of finely preserved seaweeds, the eurypterids herewith described, and the following graptolites: Dicellograptus gurleyi Lapworth, Climacograptus bicornis Hall, Climacograptus bicornis var. peltifer Lapworth, Cryptograptus tricornis (Carruthers), the first three forms in great abundance. This graptolite association is one of undoubted Normanskill age. The seaweeds occur in large perfect fronds^[1] and are of the same type as those in the Schenectady shale. The eurypterids also are strikingly similar to those from the Schenectady beds.

In one case (Pterygotus ? nasutus) we have been unable to distinguish the Schenectady and Normanskill types. This striking similarity of the two faunas (one of Chazy, the other of Trenton age) amounting almost to identity, seems to indicate a very slow progressive development of the eurypterid faunas, probably owing to their early

↑ More or less shapeless patches of these seaweeds and possibly also of eurypterid integument from the Normanskill shale at Kenwood near Albany were described by R. P. Whitfield [Am. Mus. Nat. Hist. Bul., v. 1, no. 8, 1886, p. 346, pl. 35] as Rhombodictyon and referred to the sponges on account of an apparent spongelike fibrous structure consisting, according to Whitfield, of two or three sets of rods, the principal ones of which are "straight, rigid and apparently cylindrical." This peculiar structure is shown by all the thicker specimens from the shale of the Broom street quarry and is there obviously only a system of parallel shrinkage or cleavage cracks found wherever the carbonaceous films become rather thick; and is entirely independent of outlines of the fossil but strictly parallel on all fossils of the same slab, thereby indicating its connection with a latent cleavage of the folded beds. The parallel main cracks are connected by more irregular cross cracks, the whole forming a very deceptive pattern. Sometimes these cracks have become secondarily filled by calcite or pyrite and the carbonaceous matter subsequently destroyed, whereby an apparent spongelike system of rods has resulted. Inspection of Whitfield's types in the American Museum of Natural History has shown that the types of the two species of Rhombodictyon are of quite the same nature as the thick carbonaceous patches of seaweeds from the shale at Catskill.

[1] More or less shapeless patches of these seaweeds and possibly also of eurypterid integument from the Normanskill shale at Kenwood near Albany were described by R. P. Whitfield [Am. Mus. Nat. Hist. Bul., v. 1, no. 8, 1886, p. 346, pl. 35] as Rhombodictyon and referred to the sponges on account of an apparent spongelike fibrous structure consisting, according to Whitfield, of two or three sets of rods, the principal ones of which are "straight, rigid and apparently cylindrical." This peculiar structure is shown by all the thicker specimens from the shale of the Broom street quarry and is there obviously only a system of parallel shrinkage or cleavage cracks found wherever the carbonaceous films become rather thick; and is entirely independent of outlines of the fossil but strictly parallel on all fossils of the same slab, thereby indicating its connection with a latent cleavage of the folded beds. The parallel main cracks are connected by more irregular cross cracks, the whole forming a very deceptive pattern. Sometimes these cracks have become secondarily filled by calcite or pyrite and the carbonaceous matter subsequently destroyed, whereby an apparent spongelike system of rods has resulted. Inspection of Whitfield's types in the American Museum of Natural History has shown that the types of the two species of Rhombodictyon are of quite the same nature as the thick carbonaceous patches of seaweeds from the shale at Catskill.

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