48 GEOLOGY OF THE THIRD DISTRICT. 



rock at that place, but that genus has not been seen by the reporter in any lower rock than 

 the Schoharie grit. . 



Of lingulas, two are found in this limestone : one small, the Egg-form lingula (Lingola 

 ovata) ; the other large, not yet named scientifically, artd may be called the Trenton lingula, 

 being confined to this rock. 



The beginning of perfectly preserved trilobiles, as to the upper part of their extemJil form, 

 is in this rock. These first-formed, many-jointed, mailed bodies, must play an important 

 part in the plan of creation, having held as it wore the world to themselves, reigning without 

 a competitor, during a greater part of the long period in which we find they had existence ; 

 for there is no evidence that any organic being greater than themselves, and endowed with 

 an equal locomotive power, existed from the period of the Calciferous group to that of the 

 Onondaga-salt group. 



Next in abundance to the Giant isotelus (I. gigas) of the wood-cut, is the. Senior caly- 

 mene (Calymene senaria), being the first of the genus as to age. It is of frequent occur- 

 rence, especially towards the Mohawk, being more rare north of Trenton falls. Heads and 

 tails are in some places very numerous, particularly in the neighborhood of Middleville. 

 There are two species in this rock, which are blended .together in descriptions, but never- 

 theless require separation. 



The Tessellated cryptolithus (Cryptolithus tessellatus), begins in the Trenton limestone, 

 and ends with it, if, as Dr. Emmons supposes, the one of the Salmon river series be different. 

 The remains of this trilobite exist in great numbers near the railroad station at Tripes hill. 

 Millions of heads must be there entombed, not one of which was seen with its body, nor are 

 the parts of the body or tail readily observable. They occur also near Fonda, and in the first 

 district at Glen's falls, in the same state ; showing that they were not suddenly enveloped, 

 or the lost parts would have been preserved. 



In this very brief account of some of the fossils of this remarkable rock and period of the 

 world's histcrj', our object has not been to give an account of its paleontology, but to notice a 

 few only, and those which readily serve to distinguish this rock, leaving all the other fossils 

 for their proper department of the survey ; and for a sinnlar reason, many species are omitted, 

 which have been described in former annual reports. 



By the aid of fossils collected from the Trenton limestone, I was enabled, fifteen years 

 ago, to connect the lowest limestone of the State of Ohio, with this rock ; and also the mass 

 which forms the upper part of the cliff at Frankfort, Kentucky, and of the bluff at Nashville, 

 Tennessee ; under which, in both the latter places, is well characterized birdscye limestone. 



The dark-colored limestone, as it appears at Trenton falls, or in other words, the yrell- 

 characterizcd Trenton limestone in all respects, rests immediately upon the calciferous sand- 

 rock, both at the falls back of Spraker's basin, and Canajoharic creek ; but at Fort-Plain, 

 Comstock's quarry west of Little-Falls, and at many other localities, it rests upon the birdseyc, 

 and without the slightest intermixture of the two rocks. At Fort-Plain, the surface of the 

 upper layer of the birdseyc is in "parts covered with the fossils of the Trenton rock, not one 

 of which appear below that surface. This fact shows a lapse of time between the two 



