INVERTEBRATE PALEONTOLOGY. 39] 



is very important thai the individual specimens compared should be as nearly 

 as possible of the same size: or thai the septa compared should in each shell 

 occupy a position where the diameters of the whorls are the same, or very 

 nearly the same. The reason for this precautionary advice is, that in all of 

 this great group of extinct types with more or less complex septa, the 

 sutures, or edges, of the septa became more divided and subdivided as long 

 as the shell continued to grow. In the very young, tor instance, the lobes 

 and sinuses of a species that became remarkably ramose in large adults, may 

 be merely represented by simple undulations: while individuals of interme- 

 diate sizes will show all intermediate gradations of complexity in their 

 sutures: though a practiced eye will see a general plan of structure running 

 through the whole series. It should also be remembered that where an 

 individual has, from any cause, been dwarfed in its growth, although it may 

 have attained adult age betbre death, its septa will generally be found to be 

 as simple in their structure as those of a young shell of the same species and 

 size. Again, it should be remembered that, even in specimens of the same 

 size, belonging to the same species, there will also be differences in the 

 minor details of the lobes and sinuses; while, in other cases, species clearly 

 distinguished by external characters of form and ornamentation, may have 

 the septa very similar. 



From these remarks, it will be readily seen that great caution. and 

 considerable experience are necessary in founding species on small differences 



in the sutures. 



Genus BACULITE3, Lamarck. 



Synon—Baculites, Lamarck (1799), Prodr., 80; ami ( L801 | Syst, An., m;.- Eoissy (1805), Mull., V, 33..— 

 Montforfc (1803), Conch. Syst., 1, 346.— Defrance (1816), Diet, s, i. Nat., Ill, Suppl., 

 159.— Desinarest (1817), Journ. l'liys., LXXXV, 45.— Ferussac (1819), Tab. Syst., 

 XXX — De Haan, Monogr. Auim. et Goniat., 51.— Blaiuv. (1828), .Malar., 380.— J. Sow- 

 crby (1828), Mm. Comb., VI, 186.— Say (1821), Am. Jouru. Set. and Arts, II, 41.— 

 Morton (1829), Journ. Acad. Nat. Sci. Philad., VI, 89 and 196; also (1830), Am. Journ. 

 Sci. ami Arts, 249 ; and (1834) Syuop. Org. Remains Cret. Foi ru. U. S., 42.— Desb. (1830), 

 Encyc. Meth., II, 10C and 326.— Owen (1838), Trans. Zool. Soc, II, 2.— G. B. Sowerby 

 (1842), Concb. Man. (2d ed.), 79.— D'Orbigny (1841), Paleont. Franc., Terr. Cret,, 1, 

 5.-,s._Geinitz (1845), Grumlr. .1. Verst., 306.— Hall and Meek (1856), Mem. Am. Acad. 

 Arts and Sci. Boston, V, 398— Gabb (1864), Palasont. California, 1,80; ami (1869) ib., II, 

 145 and 214.— Stoliczka (1865), Palseont. Indica, I, 196.— Favre (1870), Moll. Cram Env. 

 Leiuberg, 27 ; ami of numerous other authors. 

 Bowaloceratites (sp.), Hiipsch (ITCs), Nine Entdccliungen.III, 110. 



Eti/m. — Bacillus, a stall'. 

 Type.—BaciiUlca Fcr'cbrij'm, Lamarck. 



Shell slender, or very elongate-couoidal, more or less compressed later- 

 ally, straight, or very rarely a little arcuate along the non-septate portion; 

 aperture ovate-subtrigonal, or subcircular: lip thin, more or less deeply 



