54 PALfONTOLOOT OF NEW-YOBK. 



Oends GO'S lOCEB. as (Fam. Orthocerata). 

 [ Greek, yoviof, an angle, and xsfog, a horn] 



Character. General form and structure of the Orthoceras ; the tube flattened, with 

 extremely salient angles ; septa sinuous ; section an^xtended ellipse, with projecting 

 angles ; siphuncle ventral. 



This genus is constructed to include a very peculiar form of the Orthocerata figured on 

 Plate XIV., and which differs so essentially from all the other forms examined as to require 

 separation. 



88. 1. GONIOCERAS ANCEPS. 



Pl. XIV. Figs. 1, 1 a, b, c,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 laminae, 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 Gomiatites. 



