40: [Assembly 



longed in; two sharp lateral points; Orthis, whicli has also a 

 straight hinge-line, but is rounded on the other sides into a form 

 approaching a semicircle ; Atrypa or Rhynchonella, in which 

 the shell approaches a globular form ; Strophomena or Lept-sina, 

 in which the shell is thin, nearly semicircular in outline, and bent 

 so as to be convex on one surface and concave on the other ; and 

 various other forms. The characters here given relate merely to 

 general external appearances ; but the distinctions on which the 

 divisions of the various genera more strictly depend, are made 

 from peculiarities of the inner organization of the shells and 

 their tenants. In most of the genera there is an aperture near 

 the hinge of the shell, whence a muscular cord or " byssus " pro- 

 ceeded, by which the shell was attached or anchored to rocks or 

 other substances. 



In the Chazy limestone are also found several kinds of fossil 

 corals, but they are not abundant in comparison with those of 

 higher strata ; and a few remains of crinoids and trilobites, of 

 both which remarkable forms some account will be given in 

 speaking of the Trenton limestone, page . There are also 

 found in it some species of Orthoceras ; for a general notice of 

 which family of shells, see the Black-river limestone. 



The woodcut (Fig. 3), taken from Pr. Emmons's Beport on the 

 Third or Northern district, shows a few of the more remarkable 

 fossil shells from the Chazy limestone. No. 1 is the Scalites 

 angulatus* ; No. 2, Raphistoma staminea; No. 3, RapMstoma 

 striata; No. 4, Bucania sulcatina; No. 5, Discina deformis ; No. 6, 

 an unnamed Jitrypa.-f 



The rock which succeeds the Chazy limestone is one well 



* The names given to fossils are taken from the Greek and Latin, and are always intended 

 to be descriptive of them : thus, Scalites angulatus alludes to the spiral form of the shell 

 like a winding stair, and to its sharp external corner or angle ^ Mucania refers to the trumpet- 

 formed aperture of the shell ; Discina, to the circular form of another ; Leptcona, to the 

 thin form of another still. So among the trilobites, Isotelus implies " equal-ended,'' allud- 

 ing to the form of the fossil ; Trinucleus refers to the three knobs or elevations on the 

 buckler of the trilobite bearing the name, etc. etc. Much fault is found by many readers 

 with these hard words ; but the task of the scientific describer is not easy, when he has to find 

 names for hundreds of new objects, and he may be excused for inventing some which are not 

 euphonious. The frequent alteration of such names, growing out of the descriptions of their 

 subjects by different writers, and out of new arrangements and systems, is, however, a serious 

 evil, and tends to no little confusion in this as well as other branches of natural science. 



f But a very small part of the many hundred fossils of the New York rocks can be men- 

 tioned in this brief article. The reader is referred to the cases in the collection, where he 

 will find labeled specimens of most of the species; and also to Prof. Hall's Paleontology of 

 New York, which gives careful and full descriptipns and figures of every known relic from 

 tihese old sea-sediments. 



