12 SYNOPSIS OF THE CHARACTERS OF THE 



If this be a species of Phragmoceras, it must have been nearly as involute as P. naut ilium; on the other 

 hand, in the absence of chambers, the portion preserved bears some resemblance to certain of the silurian 

 Euomphali, as E. lineatus, but from all those it is distinguished by the small size of the inner or ventral curve, 

 and in eitlier case the species is easily known by its c\ose,Jiexuous, thread-hkc strias. 



Family NAUTILIDtE. 



1st. The genus Nautilus may be viewed as the type of the whole ; the species it contains are large, simply 

 formed shells, having a very wide geological range ; they are involute, the last chamber usually enveloping 

 all the rest, and being large enough to contain the animal ; the septa are simple, or entire at their edges, and 

 concave outwardly ; the siphuncle is discontinuous, and usually central. I have separated two groups, Temno- 

 cheilus and Discites, the characters of which will be given under those heads. 2nd. Seems to be the genus 

 Goniatites, De Haan, which has the edges of the septa bent angularly, so as to assume a complexity little short 

 of what we see in the true Ammonites. 3rd. Bellerophon, although strongly allied to Argonauta, may, per- 

 haps, be left in this family for the present, on account of the greater thickness of the shell, and its larger and 

 more perfectly formed spire. The genus Phragmoceras of Brodrip, appears to belong to the present family, 

 rather than to the Orthoceratida, to which, however, it obviously approaches ; the compressed, curved form 

 of these shells is very different from that of Orthoceras, but approaches closely to what might be considered 

 as a partially unrolled Nautilus, from which it differs in no very important point of structure; some of the spe- 

 cies are almost perfectly involute, as the P. naiitilium. 



Goniatites. De Haan. 



Gen. Ch.- — Shell discoid, involute; edges of the septa bent into distinct angles ; siphuncle dorsal. 



This remarkable genus appears to be characteristic of the carboniferous series (including the carb. slate 

 or upper Devonian). It is found in every marine member of this group, and in some of them it is the most abun- 

 dant fossil, while neither above nor below do we find any shells possessing the peculiar structure of the genus. 



Goniatites Browni. MCoy. (PL IV. fig. 17). 



Sp. Ch. — Discoid, subglobose, sides flattened ; umbilicus large, acute-edged, exceeding one-third the 

 diameter of the shell ; surface smooth ; septa, dorsal lobe small, bifid ; dorsal sinus acute ; first lateral lobe slightly 

 exceeding the dorsal in length, very wide, rounded ; lateral sinus twice as long as the dorsal, acute, linguiform ; 

 second lateral lobe very wide, obtusely rounded. 



From the G. striatus. Sow., which the species most resembles, it is distinguished internally by its much 

 shorter and wider first lateral lobe ; the same character distinguishes it from the G. sphcericus, Sow., and from 

 both it is distinguished externally by its smooth surface, and from all the species of the same form, by the large 

 size of the umbilicus. Diameter two inches two Hues, thickness one inch one line. 



Goniatites crenistria. Phil. 



Goniatites crenistria. — P/iil. GeoL York. 



Sp. Ch Spheroidal, umbilicus very small ; surface with delicate, slightly waving, transverse stria, which 



are crenulated by very fine spiral lines. 



This beautiful shell is completely reticulated by the crossing of the most delicate spiral and transverse 

 striae ; it varies considerably in shape, being sometimes almost spherical, and at other times compressed ; the 

 markings of the sm-face will, however, at all times distinguish it ; the septa are exactly similar to those of the 

 G. striatus ; diameter one and a half inches, thickness ten lines. 



