RlJEDEMANN SESSILE CoNULARIA. 



710 



cations of transverse ridges winch suggest a comparison with the surface 

 sculpture of the adult Conuldria. As these few indications of surface sculp- 

 ture in the smallest stages are, however, in contrast to the generally smooth 

 appearance of the fossils, they can hardly he regarded as reliable evidence of 

 the existence of a sculpture in this smallest stage, and may be only secondary 

 corrugations. There has, however, been found a specimen, 4 mm. long, 

 which is excellently preserved and which exhibits a system of distinct 

 intersecting longitudinal and transverse ribs (cf. PI. IV, tig. 35). The sculpt- 

 ure of this fossil differs from that of an adult individual in the appearance of 

 the transverse ribs which are not undulating but straight, and which, tow aids 

 the base, become more prominent than the longitudinal ones. The same 

 specimen possesses a peculiarity in its four deep transverse furrows. Whether 

 the latter originate from more closely arranged transverse ribs and retarded 

 growth or from the former presence of septa which are broken out, remains 

 doubtful because of lack of corroborating observations. 



Adolescent stages ranging in size between the last described and the 

 adult stage, have been described and figured on Plate I. figures 1, 2, 3, 5. 

 They show the sessile mode of life of these stages, the structure of the basal 

 cup, the presence of the surface sculpture which is characteristic of Conula/ria 

 gracilis, and the peculiar transverse ridges of the side walls of the marginal 

 grooves. 



All the forms described so far are flattened, often into a mere car- 

 bonaceous film and can not be regarded as giving conclusive evidence as to the 

 transverse section and actual general aspect of the infantile shell. This 

 defect in the material has been filled by a single fortunate discovery of a 

 small slab bearing eight young Conularias which are either not at all or but 

 slightly compressed. Two of the latter (cf. PL IV, figs. .'17 and 38) were 

 attached to a shell of Endoceras. Most of these shells, as well as the impres- 

 sions of some which are broken out, are perfectly round (cf. figs. 36 and 38) 

 and remarkably strong. The position of the marginal groove is indicated by a 

 narrow furrow. They are perfectly smooth, but as indicated by one specimen, 

 a sculptured superficial layer existed originally around the thicker interior 

 shell. Figure 37 is taken from a specimen which suffered a slight crushing; 

 as a consequence, the median part is sunken in and the stronger marginal 

 grooves appear as a projecting frame, giving also to this form the appearance 

 of a compressed pyramid. While this specimen explains why even very 

 young shells may appear as pyramids, it is shown by the 1 uncompressed 

 specimens that the original section of the youngest stage was circular. The 



