108 PALAEONTOLOGY. 



Other hand, are very flat and compressed. The lateral lobes and cells would 

 pass for those of a typical Chjdonites; but the latter are larger and more 

 numerous. In both, liowever, the superior lateral lobes are the deepest. 



" 2. — Chjdonites qiiadrangidaris and C. costatns, Hauer. 



" These have septa quite similar, but there is no agreement of form, 

 the former having involuted, squarely-shaped, rapidly-increasing whorls, 

 and the latter abdominally-depressed, non-involute, gibbous-sided, keeled 

 whorls. 



"3. — Cli/donUes spincscens and C. aniiatiis, Ilauer. 



"These are very distinct species, tlie septa differing- considerably, and 

 the forms and pilaj more. 



" 4. — Chjdonites decoratus, Ilauer, the first species mentioned by him, 

 and here viewed as the type of that genus, is decidedl}^ unique in the group; 

 the rows of tubercles on the abdomen are exceptional, although the septa, 

 if correctly drawn, are similar to those of C. spinescens. 



" 5. — Cbjdonitcs Fresei, Laube, has very singular septa, quite similar to 

 those of Ammonites Klipteinianus. The smoothness, stoutness, and involu- 

 tion of tlie whorls, however, in the latter are very different from the pileated 

 non-involute whorls of the former. 



" Tiie want of proper classification and arrangement which is thus 

 shown to exist in this natural series was very plainly perceived by its 

 describer, who asserts that it contains different types, and is capable of 

 division into different families. 



" The confusion introduced into nomenclature of the Ammonites by 

 von Buch, wlio, as a geologist, did not recognize the necessity of giving a 

 fixed value to tlie names of groups, is here repeated; and the families are 

 considered less comprehensive than the genera. 



" So little is known of the septa of the American specimens that their 

 place among the Clydonitidce appears to be doubtful, though the few lateral 

 lobes figured in the California Geological Report seem to show that they 

 belong to this division." — (A. II.) 



