188 GEOLOGICAL BIOLOGY. 



to each other and to the individual it is not necessary to 

 describe them, but symbols may be chosen to stand for them, 

 and by examining the symbols we may arrive directly at the 

 meaning of the expression ' ' origination of characters and 

 species." 



If we then express the morphological and physiological 

 characters by symbols, using the letters B for the characters 

 of the branch, C for those of the class, O for those of the 

 order, F for those of the family, G for those of the genus, 

 S for those of the species, V for the varietal characters, and 

 the numerals I, 2, 3, 4, etc., for the different types of each 

 category, we may combine these symbols in such a way as to 

 express the sum of the characters of a particular individual 

 organism. 



Spirifer striatus Martin, var. S. Logani Hall, taken as the Ex- 

 ample. The example chosen for examination is a well-known 

 fossil, specifically recognized in each of the continents in 

 limestones of Eocarboniferous age, Spirifer striatus Martin. 

 The variety which is found in the Keokuk limestones of the 

 Mississippi valley is called Spirifer Logani Hall in the " Iowa 

 Geological Report " (vol. I. pt. 2, PL XXL, p. 647). In order 

 to fully define this specimen and assign its place in the classi- 

 fication of organisms we must refer it to the branch Mollus- 

 coidea (B 6) of the Animal Kingdom* to the class Brachiopoda 

 Dumeril (C 2) and subclass Arthropomata Owen, to the 

 order Telotremata (O 4) of Beecher,f to the suborder Heli- 

 copegmata Waagen, ^ family Spirifer ides King (F4), sub- 

 family Trigonotretaria Schuchert, J genus Spirifer Sowerby^f 

 (G 10), species striatus Martin,** and variety (so-called 



*Claus and Sedgwick, " Elementary Text-book of Zoology," translated and 

 edited by Adam Sedgwick, with the assistance of F. G. Heathcote, part n. p. 71. 

 London and New York, 1884. 



f Am. Jour. Sci., sen in. vol. XLI. p. 355. 



\Palczontologia Indica, ser. xiii., " Salt Range Fossils, "by William Waagen, 

 Pt. i., " Productus-limestone fossils," iv. p. 447. Calcutta, 1883. 



Thos. Davidson, "British Fossil Brachiopoda," vol. I. p. 51. PaUonto- 

 graph. Soc. t London, 1853, etc. 



\Am. Geol., vol. n. p. 156. 



^[ Schuchert's list, Am. Geot. t vol. II. p. 156. 



** See Davidson's " Brachiopoda," vol. n Pt. V. p. 19, PI. II. and III. 



