MODERN CLASSIFICATION. 253 



were enclosed, a nearly Callovian age." Dr. Waagen has found, however, that some of 

 the Indian species range through the greater part of the Jurassic series, and " even re- 

 appear in the Upper Cretaceous beds.'' 



Genus Cosmoceras, TFaa^. — Shell flat, discoidal ; sides provided with ribs of various 

 forms, which are all bent forward, and impart a highly ornamental character to the shell ; 

 spines and tubercles are often developed therefrom. The ventral edge has some- 

 times a smooth channel in the middle, which interrupts the course of the ribs across the 

 siphonal area, as in Cosm. Parkmsoni, Sow., and Cosm. Garantiaimm, d'Orb. The body- 



FiG. 163. — Cosmoceras Duncani, Sow. Fig. 1G4. — Cosmoceras Jason, Re'mecke. Fig. 165. — Cosmoceras radiatum, Bruguiere. 



chamber is about half the length of a whorl. The mouth-border develops lateral 

 auricles in youth, which disappear in old age. The suture-line is very much ramified. 

 The siphonal lobe often equals, but is sometimes shorter than the principal lateral, which 

 is large and branched ; the second lateral is small, and there are several auxiliaries. The 

 Aptyclius is the same as in Stephanoceras. 



This genus appears first in the upper beds of the Inferior Oolite with Cosm. 

 Parkinsoni, Sow., and Cosm. Garantianum, d'Orb. In the Kelloway Rock and Oxford 

 Clay are several other species, as Cosm. Calloviense, Sow., Cosm. Buncani, Sow. (fig. 163), 

 Cosm. Koenigi, Sow., Cosm. Gowerianum, Sow., Cosm. Jason, Rein. (fig. 164), Cosm. Julii, 

 d'Orb.; in the Chalk by Cosm. verrucosum, d'Orb., Cosm. radiatum, Brug. (fig. 165). 



Genus Ancyloceras, d'Orbic/. — Shell spiral, rolled on the same plane, with few 

 whorls, all of which are disjointed and separate from each other ; the last projected out- 

 wards in a horizontal line, and then turned upwards and inwards, forming an arch 

 opposed to the turns of the spire. The recurved portion without septa is the body- 

 chamber. The mouth-border is simple, round, and thickened by a shelly eversion. 

 The septa are transverse and symmetrical, divided into six lobes, which are very unequal 

 in size, and formed of very ramified, elongated digitations. 



This genus first appeared in the Jurassic seas ; in the upper beds of the Inferior 



