yA CEPHALOPODA. GONIATITES. 
It may be considered as a straight Ammonite ; for, as in that genus, the 
transverse plates are sinuous, and terminate in foliated dentations at their 
union with the external shell. The species of this genus are found in the 
Cretaceous formation alone. 
Buckland remarks, it is a singular circumstance, that this straight modifica- 
tion of the form of Ammonites should not have appeared until this family had 
reached the last stage of the secondary deposits, throughout which it has 
occupied so large an extent; and that, after a comparatively short duration, 
the Baculite should have become extinct simultaneously with the last of the 
Ammonites, at the termination of the Chalk formation. 
The outer shell of the Baculites is thin, but, like that of the Ammonites, is 
strengthened by oblique ribs; near the posterior margin of the shell, the 
transverse plates are penetrated by a siphuncle. This character, and the 
sinuous form, and denticulated edges, and transverse plates, are characters 
common to both this genus and Ammonites. 
Genus 1V.— TURRILITES. — Lamarck. 
Generic Character. — Shell spiral, multilocular, turreted, 
with contiguous volutions coiled around themselves in the 
form of a winding tower, and gradually diminishing towards 
the apex, the whole being perceptible; walls articulated by 
sinuous sutures; with close, transverse septa, lobed and 
laciniate at the margin; siphuncle situate near the dorsal 
margin; outer chamber large ; aperture rounded, with an 
expanded outer lip. 
Turrilites tuberculatus. Plate II. fig. 3. Found in the 
Marl stratum at Middleskam, parish of Ringmer, Sussex. 
The shells of the genus Turrilites are extremely thin, and their exterior is 
ornamented and strengthened with tubercles and ribs. They resemble in 
every respect the Ammonites, except that they are straight, with a produced 
spire, instead of being coiled. Their internal cavity is divided into many 
chambers by transverse plates with foliated edges. 
The species of this genus are known only in a fossil state. 
Genus V.— CRIOCERATITES. 
Generic Character. — Shell multilocular, convolute, with 
the volutions disunited, or not rolled upon one another. 
Crioceratites Duvallu. Plate VI. fig. 1. 
Genus VI.— GONIATITES. — Von Buch. 
Generic Character. —- Shell discoidal, generally convex 
or nearly globose ; most of the species deeply umbilicate ; 
the inner volutions much or wholly concealed, being gene- 
rally enveloped in the outer one ; provided with internal 
partitions, or septa, and lateral and dorsal lobes and sinuses ; 
siphuncle situate near the ambit ; it is not, however, a con- 
tinuous tube, but passes naturally from the septal plate a 
short distance. 
