108 Subsurface Geologic Methods 



ture, associated bone material and jaw parts, and stratigraphic occur- 

 rence; and (3) the assignment of conodonts to other zoological groups is 

 challenged because these other groups do not possess hard parts of 

 similar size and shape that are composed of calcium phosphate. 



A unique method of graphically illustrating the stratigraphic range 

 of conodonts is shown in figure 47. 



Otoliths 



Fish otoliths or earstones, which are present in many strata, are 

 neglected by many micropaleontologists in stratigraphic and paleontologic 

 investigations. These structures, consisting essentially of calcium car- 

 bonate and ranging in breadth from 0.1 to 3.0 millimeters, are secreted 

 in the auditory system of fish. 



A small one, termed the "lapillus," is formed in a portion of the labyrinth 

 known as the "utriculus" ; a second, termed the "asteriscus," is formed in a 

 posterior prolongation of the otolith-sac (sacculus), called the "lagena" ; and 

 a third, the sagitta, which is the principal earstone which occurs in the sacculus. 

 This saggita is the most important and is by far the largest in most cases.^^ 



Plate 5 illustrates the general structural implications of the sagitta. 



According to Campbell, "otoliths are admirably suited to be used 

 as a tie between sections located far apart — sections whose comparatively 

 local zones are well studied through Foraminifera, ostracoda, and other 

 microfossils." 



Otoliths were found to be useful in correlating certain phases of 

 the Middle Teritiary sequence of central Sumatra. 



Spores and Pollen 



Fossil plant spores and pollen, which represent a definite part in 

 the reproductive cycles of plants, occur in most coals, in many shales, 

 and in some of the coarser elastics. British workers have been foremost 



EXPLANATION OF PLATE 5 



Figure 



1-11, 3, 6. Otolithus var. A X 20. Figs. 1, 4, 7, 10, showing variation of inner 

 side of the right otolith. Figs 2, 5, 8, 11, showing outer side. Fig. 2, sec- 

 tion cut normal to median axis and showing elongate umbilical area. Viewed 

 from caudal end. Fig. 6, transverse section showing ovate umbilical area 

 and the radiating character of the inner part. (Terminology: DM = dorsal 

 margin ; VM = ventral margin ; CE = caudal extremity ; FE = frontal ex- 

 tremity ; AR = antirostrum ; R = rostrum ; = ostium ; CA = cauda ; + CA 

 = sulcus acusticus; CS = crista superior; A = the area; E — excisura ostii; 

 YF = ventral furrow; V = umbilicus.) 



9, 12, 13, Otolithus var. B X 20. Figs. 9, 12, inner side views showing the closed 

 character of the sulcus acusticus. Observe the prominent projections along 

 the ventral margin, which constitutes a distinctive feature of the variety. 

 Fig. 13 illustrates the radial character as well as the concentric growth lines. 



'' Campbell, R. B., Fish Otoliths, Their Occurrence and Value as Stratigraphic Markers: Jour. 

 Paleontology, vol. 3, no. 3, pp. 254-279, Sept. 1929. 



