MODERN CLASSIFICATION. 255 



growth. Body-uhamber from two thirds to an entire whorl. Lobes similar to those in 

 Stephanoceras, differing, however, in being more ramified, and having pendant columellar 

 lobes. Aptijchus bivalved, calcareous, very thin, and externally granular. Perisphindes 

 Martinsii, d'Orb. (fig. 168), from the Inferior Oolite of France and England, is geologically 

 the oldest of this group, which is largely developed in the Middle and Upper Jurassic 

 strata of Europe ; a few species are found in the Chalk. 



The genus Perisphinctes is represented in the Kachh Jura (Kutch)^ by more than 

 fifty species, which can be distributed, according to Dr. W. Waagen, into six large 

 sections, most of which comprise several groups embedded in strata which find their 

 equivalents in the Middle and Upper Jurassic rocks of Europe among the Kelloway, 

 Oxford, Corallian, Kimmeridgian, and Portlandian stages. 



Genus Olcostephanus, Neum. — This genus was erected to receive a certain number 

 of species that were formerly grouped with the preceding, but which are now separated 

 from Perisphinctes. The type of this group is Olcos. Caiitleyii, 0pp., from the Indian 

 Jura. Olcostephanus, in contrast with Perisphinctes, has a shorter body-chamber, two 

 thirds of a whorl in length. Mouth-border in some has a simple smooth band, and in 

 others lateral auricles are developed. The ribs project broadly from the border of the 

 umbilicus, and separate on the sides into many smaller branches. 



Genus Scaphites, Park. — Shell spiral, rolled on the same plane. Whorls at first 

 contiguous and united, then separated from the others and projected outwards in nearly 



ffijmrspn-jr \ 



Fio. 169. —Scaphites Ivanii, Puzos. 



a straight line, afterwards turned upwards, bent round, and curved inwards, forming a 

 kind of horse-shoe shape. The septa transverse, symmetrically and regularly divided into 

 more than six very unequal-sized lobes, invariably composed of short bilateral ramifications ; 

 the saddles formed of bladder-like cells. The siphonal lobe is as long as the principal 

 lateral. The form of the inner whorls of Scaphites corresponds with those of Olcostephanus. 

 Mouth-border round or oval, provided with large protuberant bands more or less 

 prominent. All the species are found in the Cretaceous rocks. Scaphites gigas. Sow. 



1 ' PalEeoutologia Iiidica ;' " Jurassic Fauna of Kutch," p. 143, 1875. 



