Geological Equivalents. 135 



questionable cases and controverted points. Perhaps 1 may here- 

 after occupy a few pages of this Journal with a condensed series of 

 facts, in support of a general nomenclature of American geology. In 

 this I intend to point out the agreement, announced to the public by 

 myself, fourteen years ago, which was discoverable in almost all the 

 deposits of both continents ; and the few points of total disagree- 

 ment — particularly the Chalk of Europe and Ferriferous rocks of 

 America. I intend to refer chiefly to organized remains ; the study 

 of which, I believe I happened to be the first to introduce, into an 

 American geological school, in the year 1818.* 



* Want of books, (or rather of persons qualified for making them,) in every part 

 of the world, kept back this department of knowledge, several years after a taste for 

 the study was strongly excited. Such however was the zeal of my students, that I 

 was driven to the work of giving names to our specimens, excepting those which I 

 could make out by the Linnean descriptions, (which I translated and published eleven 

 years ago,) and a few labelled by Le Sueur. By these means we could understand 

 each other, in our own school ; while we waited, impatiently, for competent author- 

 ities. I must ask to be excused, for using some of my own descriptive names in this 

 article, for our species of Encrinus ; as the parts assumed by authors for characters 

 are rarely present. A recent specimen in the Albany museum, found among the 

 rubbish of the New Haven museum, formerly kept by Mix, (probably from the 

 West Indies,) is the only one, whether a relic or recent, ever seen in America, as far 

 as I know, which contains those characters. I have, I believe, two undescribed 

 Trilobites and a Lichen, to which I give temporary names also. I will give the old 

 names (if named) as soon as I am able. 



Encrinus transversus. — Always perforates strata transversely; rings low. 

 Found in the lowest and compact layer of metalliferous lime-rock, — called Encrinal 

 rock by Conybeare, and bird's-eye marble by stone-cutters. 



E. dicyclus. — Pairs of low rings alternating with single high ones. Found in 

 second graywacke. 



E. giganteus. — Branching, and of great length. Found in saliferous rocks. 

 E. interruptus. — High rings interrupted by single and double low ones. Found 

 in coral rag. 



E. teretiformis. — Tapering rapidly, rings even, generally pale or white. Found 

 in coral rag. 



E. curvatus. — Rings distinct, with their edges double ; always curved, and lying 

 between layers. Found in shell limestone, at Glenn's Falls. 



Cenomice muscioides. — Stipes cespitose, sub-cylindrical, fistulous, bearing leaves 

 or processes, sometimes arranged spirally, or densely scattered on all sides. Found 

 in stratified tufa, in layers, in and under shell marl. 



Cancer trilobioides. — Length and breadth nearly equal; side lobes one sixth 

 the breadth of the middle lobe; joints four, posterior one broadest and cleft on the 

 upper side. About half an inch in length. Found in second graywacke slate (coal 

 slate) on the Mohawk river, where the Erie Canal is cut through the rock. Bears 

 a strong resemblance to the trilobites. A carbonate of lime covering is very entire 

 on some specimens. The incurved tail of Brongniart's Cancer punctulatus resem- 

 bles this petrifaction. Probably all the animal was very perishable, but the thick 

 crustaceous tail ; which is all that now remains. 



