TRENTON LIMESTONE. 77 



to me in the lower term of our system, and on tliis account is more interesting, as showing- 

 the early commencement of this peculiar form of coral, which is known only in a fossil 

 state. The lowest position in which it has been known previously, is the Wenlock limestone, 

 and the upper limestone of the Caradoc ( Siluria?! System, p. 676 ) ; others occur in the 

 Eifel (Devonian), and other species are known in the Oolite and Jura limestones. 



This is not aconmion fossil in the Trenton limestone, though it has been seen in several 

 localities widely separated, thus proving its great geographical range. 



Fig. 6 a. The dorsal valve of Ddlhyris lynx, having the inner side of the shell spread ovrr with a fine 



web of this little coral. 

 Fig. 6 i. A magnified portion, showing the form of the cells, openings, etc. 

 Fig. 6 c. Two of the cells still farther magnified. The openings and structure, in these portions, are 



more like Alecto than Aulopora. 



Position and locality. In the blue shaly limestone of Ohio and Kentucky, equivalent to 

 the Trenton limestone of New-York. 



117. 1. ALECTO INFLATA. 



Pl. XXVI. Figs. 7 a, b. 



Coral attached, arachnoid ; tubes short, much expanded above, contracting at the aper- 

 ture, and narrowing rapidly below ; mouths large, opening obliquely upwards. 



This coral resembles the last in its mode of growth and general appearance ; but the 

 tubes are more expanded or vesicular above, and the little mouths arc proportionally more 

 distinct. It is clearly referrible to the Genus Alecto, in its mode of growth, form, and 

 arrangement of cells, which proceed one from the other, each base being a little below the 

 aperture of the previous one. 



Fig. 7 a. Dorsal valve of Leplana alternata, on the outer surface of which this coral is affi.xed. 

 Fig. 7 b. Two of the tubes magnified, to show their form. 



Position and locality. This coral occurs in the central part of the Trenton limestone, 

 associated with the Trilobites, Brachiopoda and Orthoccrata of the rock. Trenton Falls, 

 Oneida county. 



118. 1. INTRICARIA? RETICULATA. 



Pl. XXVI. Figs. S a, b, c. 



Coral composed of a great number of filiform cylindrical branches, which anastomose 

 irregularly, and spread over a considerable surface, apparently attached to some other body ; 

 cells in a single row on the upper side of the branches ; mouths of the cells circular or 

 slightly oval. 



