54 PALEONTOLOGY OF NEW-YORK. 
Genus GONIOCERAS (Fam. Orthocerata ). 
[ Greek, yovios, an angle, and xépas, a horn] 
Character. General form and structure of the Orruocrras; the tube flattened, with 
extremely salient angles; septa sinuous; section an extended ellipse, with projecting 
angles; siphuncle ventral. 
This genus is constructed to include a very peculiar form of the OrTHoceRatTAa figured on 
Plate XIV., and which differs so essentially from all the other forms examined as to require 
separation. 
88. 1. GONIOCERAS ANCEPS. 
Pu. XIV. Figs. 1, 1 a, 6, ¢, d. 
General form elongated, somewhat rapidly tapering from the base, extremely compressed ; 
section an excentric ellipse, compressed laterally towards the extremities, and extended into 
very acute angles ; diameters as 1 to 4 or 1 to 5; septa composed of double lamine, deeply 
concave in the centre, numerous, thin, approximate, sinuous on the longest diameter ; 
siphuncle moniliform, ventral, consisting of a round tube, which is exceedingly expanded 
between the septa, like the siphuncle of OrMocERas. 
This remarkable fossil, usually appearing upon the weathered surfaces of rocks, with 
the ventral or dorsal side exposed, and presenting a broad surface with extended septa and 
central siphon, has received the appellation of ‘‘petrified fish’s backbones.”? I had been 
disposed to regard this structure (as represented in the plate) as due, in part at least, to 
pressure ; but the examination of numerous specimens in the rock, and of a portion of one 
nearly perfect, compels me to decide that their apparent disproportions are natural, and not 
the result of accident. In a portion of a nearly perfect individual, the siphuncle is so near 
the outer shell as to produce a longitudinal ventral ridge. In this instance, the relative 
diameters confirm previous measurements. 
The shell is apparently smooth or very finely striated, and extremely thin, as also are 
the septa. There is very little evidence of compression, and the original form seems to have 
been very nearly what it now is. 
In the longest diameter of the ellipse, the septa bend rapidly forward from the siphuncle, 
till a little more than half way to the external shell, where they make a gentle curve more 
directly towards the exterior, and, before reaching it, curve a little backwards. In the 
opposite direction, the septa have but a simple curve. In this character, the septa bear some 
resemblance to those of GonIATITES. 
